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ASP.NET MVC 6 Hosting - HostForLIFE.eu :: FileResult In ASP.NET Core MVC

clock May 13, 2020 09:18 by author Peter

This article is an overview of FileResult in ASP.Net Core MVC. The FileResult actions are used to read and write files. FileResult is the parent of all file-related action results. There is a method on ControllerBase class called File. This method accepts a set of parameters based on the type of file and its location, which maps directly to the more specific return types. I’ll discuss how to use all the FileResult actions available in ASP.Net Core MVC.

There are different type of file results in core MVC.
FileResult
FileContentResult
FileStreamResult
VirtualFileResult
PhysicalFileResult

FileResult

FileResult is the parent of all file-related action results. It is a base class that is used to send binary file content to the response. It represents an ActionResult that when executed will write a file as the response.

public FileResult DownloadFile() 

     return File("/Files/File Result.pdf", "text/plain", "File Result.pdf"); 


FileContentResult
FileContentResult is an ActionResult that when executed will write a binary file to the response.
public FileContentResult DownloadContent() 

            var myfile = System.IO.File.ReadAllBytes("wwwroot/Files/FileContentResult.pdf"); 
            return new FileContentResult(myfile, "application/pdf"); 


FileStreamResult

FileStreamResult Sends binary content to the response by using a Stream instance when we want to return the file as a FileStream.
public FileStreamResult CreateFile() 

   var stream = new MemoryStream(Encoding.ASCII.GetBytes("Hello World")); 
   return new FileStreamResult(stream, new MediaTypeHeaderValue("text/plain")) 
   { 
      FileDownloadName = "test.txt" 
   }; 


VirtualFileResult
A FileResult that on execution writes the file specified using a virtual path to the response using mechanisms provided by the host. You can use VirtualFileResult if you want to read a file from a virtual address and return it.
public VirtualFileResult VirtualFileResult() 

    return new VirtualFileResult("/Files/PhysicalFileResult.pdf", "application/pdf"); 


PhysicalFileResult
A FileResult on execution will write a file from disk to the response using mechanisms provided by the host.You can use PhysicalFileResult to read a file from a physical address and return it, as shown in PhysicalFileResult method.
public PhysicalFileResult PhysicalFileResult() 

   return new PhysicalFileResult(_environment.ContentRootPath + "/wwwroot/Files/PhysicalFileResult.pdf", "application/pdf"); 


Step 1
Open Visual Studio 2019 and select the ASP.NET Core Web Application template and click Next.

Step 2
Name the project FileResultActionsCoreMvc_Demo and click Create.

Step 3
Select Web Application (Model-View-Controller), and then select Create. Visual Studio used the default template for the MVC project you just created.

Step 4
In Solution Explorer, right-click the wwwroot folder. Select Add > New Folder. Name the folder Files. Add some files to work with them.

Complete controller code
using Microsoft.AspNetCore.Hosting; 
using Microsoft.AspNetCore.Mvc; 
using Microsoft.Net.Http.Headers; 
using System.IO; 
using System.Text; 
 
namespace FileResultActionsCoreMvc_Demo.Controllers 

    public class HomeController : Controller 
    { 
        private readonly IWebHostEnvironment _environment; 
 
        public HomeController(IWebHostEnvironment environment) 
        { 
            _environment = environment; 
        } 
        public IActionResult Index() 
        { 
            return View(); 
        } 
 
        public FileResult DownloadFile() 
        { 
            return File("/Files/File Result.pdf", "text/plain", "File Result.pdf"); 
        } 
 
        public FileContentResult DownloadContent() 
        { 
            var myfile = System.IO.File.ReadAllBytes("wwwroot/Files/FileContentResult.pdf"); 
            return new FileContentResult(myfile, "application/pdf"); 
        } 
 
        public FileStreamResult CreateFile() 
        { 
            var stream = new MemoryStream(Encoding.ASCII.GetBytes("Hello World")); 
            return new FileStreamResult(stream, new MediaTypeHeaderValue("text/plain")) 
            { 
                FileDownloadName = "test.txt" 
            }; 
        } 
        public VirtualFileResult VirtualFileResult() 
        { 
            return new VirtualFileResult("/Files/PhysicalFileResult.pdf", "application/pdf"); 
        } 
 
        public PhysicalFileResult PhysicalFileResult() 
        { 
            return new PhysicalFileResult(_environment.ContentRootPath + "/wwwroot/Files/PhysicalFileResult.pdf", "application/pdf"); 
        } 
 
    } 


Step 5
Open Index view which is in views folder under Home folder. Add the below code in Index view.
Index View
@{ 
    ViewData["Title"] = "Home Page"; 

 
<h3 class="text-center text-uppercase">FileResult Action in core mvc</h3> 
<ul class="list-group list-group-horizontal"> 
    <li class="list-group-item"><a asp-action="DownloadFile" asp-controller="Home">File Result</a></li> 
    <li class="list-group-item"><a asp-action="DownloadContent" asp-controller="Home" target="_blank">File Content Result</a></li> 
    <li class="list-group-item"><a asp-action="CreateFile" asp-controller="Home">File Stream Result</a></li> 
    <li class="list-group-item"><a asp-action="VirtualFileResult" asp-controller="Home" target="_blank">Virtual File Result</a></li> 
    <li class="list-group-item"><a asp-action="PhysicalFileResult" asp-controller="Home" target="_blank">Physical File Result</a></li> 
</ul> 


Step 6
Build and run your Project ctrl+F5



ASP.NET MVC 6 Hosting - HostForLIFE.eu :: HTML Helpers In ASP.NET MVC

clock April 9, 2020 05:10 by author Peter

What is an Html Helper?
Html helper is a method that is used to render HTML content in a view. Html helpers are implemented using an extension method. If you want to create an input text box with

id=email and name in email:
  <input type=text id=email name=email value=’’/> 


This is all the Html we need to write -- by using the helper method it becomes so easy:
  @Html.TextBox(‘email’) 

It will generate a textbox control whose name is the email.

If we want to assign the value of the textbox with some initial value then use the below method:
  @Html.TextBox(‘email’,’sagar@gmail.com’) 

If I want to set an initial style for textbox we can achieve this by using the below way:
  @Html.TextBox(‘email’,’sagar.jaybhay@gmail.com’,new {style=’your style here’ , title=’your title here’});  

Here the style we pass is an anonymous type.

If we have a reserved keyword like class readonly and we want to use this as an attribute  we will do this using the below method, which means append with @ symbol with the reserved word.
  @Html.TextBox(‘email’,’sagar.jaybhay@gmail.com’,new {@class=’class name’, @readonly=true}); 

If we want to generate label:
  @Html.Label(‘firstname’,’sagar’) 

For password use the below Html helper method to create password box:
  @Html.Password(“password”) 

If I want to generate a textarea then for this also we have a method:
  @Html.TextArea(“comments”,”,4,12,null)  

In the above code 4 is the number of rows and 12 is the number of columns.

To generate a hidden box:
  @Html.Hidden(“EmpID”) 

Hidden textboxes are not displayed on the web page but used for storing data and when we need to pass data to action method then we can use that.

Is it possible to create our Html helpers in asp.net MVC?

Yes, we can create our Html helpers in MVC.

Is it mandatory to use Html helpers?

No, we can use plain Html for that but Html helpers reduce a significant amount of Html code to write that view.
Also, your code is simple and maintainable and if you require some complicated logic to generate view then this is also possible.



ASP.NET MVC 6 Hosting - HostForLIFE.eu :: Partial View in MVC

clock March 20, 2020 12:00 by author Peter

Partial view in ASP.NET MVC is special view which renders a portion of view content. It is just like a user control of a web form application. Partial can be reusable in multiple views. It helps us to reduce code duplication. In other word a partial view enables us to render a view within the parent view.
 

The partial view is instantiated with its own copy of a ViewDataDictionary object which is available with the parent view so that partial view can access the data of the parent view. If we made the change in this data (ViewDataDictionary object), the parent view's data is not affected. Generally the Partial rendering method of the view is used when related data that we want to render in a partial view is part of our model.
 
Creating Partial View
To create a partial view, right-click on view -> shared folder and select Add -> View option. In this way we can add a partial view.
 

Creating Partial View
It is not mandatory to create a partial view in a shared folder but a partial view is mostly used as a reusable component, it is a good practice to put it in the "shared" folder.

HTML helper has two methods for rendering the partial view: Partial and RenderPartial.
    <div> 
        @Html.Partial("PartialViewExample") 
    </div> 
    <div> 
        @{ 
            Html.RenderPartial("PartialViewExample"); 
        } 
    </div>

@Html.RenderPartial
The result of the RenderPartial method is written directly into the HTTP response, it means that this method used the same TextWriter object as used by the current view. This method returns nothing.
 
@Html.Partial
This method renders the view as an HTML-encoded string. We can store the method result in a string variable.
 
The Html.RenderPartial method writes output directly to the HTTP response stream so it is slightly faster than the Html.Partial method.
 
Returning a Partial view from the Controller's Action method:
    public ActionResult PartialViewExample() 
    { 
        return PartialView(); 
    }

Render Partial View Using jQuery
Sometimes we need to load a partial view within a model popup at runtime, in this case we can render the partial view using JQuery element's load method.
    <script type="text/jscript"> 
            $('#partialView').load('/shared/PartialViewExample’); 
    </script>



ASP.NET MVC 6 Hosting - HostForLIFE.eu :: Modal Popup In MVC Application

clock February 28, 2020 11:15 by author Peter

In this post we will implement modal pop up to display the detailed information of user after clicking on detail anchor. So this is the view on which we are going to apply modal popup.

View code
Enumerable<CodeFirst.Models.FriendsInfo> 
 
@{ 
    ViewBag.Title = "Index"; 

 
<h2>Index</h2> 
 
<p> 
    @Html.ActionLink("View All", "Index") 
 
    @using (Html.BeginForm("Search", "Home", FormMethod.Post)) 
    { 
        <table> 
            <tr> 
                <td> 
                    <input type="text" id="txtName" name="searchparam" placeholder="type here to search" /> 
                </td> 
                <td> 
                    <input type="submit" id="btnSubmit" value="Search" /> 
                </td> 
            </tr> 
        </table> 
    } 
 
</p> 
<table class="table"> 
    <tr> 
        <th> 
            @Html.DisplayNameFor(model => model.Name) 
        </th> 
        <th> 
            @Html.DisplayNameFor(model => model.Mobile) 
        </th> 
        <th> 
            @Html.DisplayNameFor(model => model.Address) 
        </th> 
        <th></th> 
    </tr> 
 
    @foreach (var item in Model) 
    { 
        <tr> 
            <td> 
                @Html.DisplayFor(modelItem => item.Name) 
            </td> 
            <td> 
                @Html.DisplayFor(modelItem => item.Mobile) 
            </td> 
            <td> 
                @Html.DisplayFor(modelItem => item.Address) 
            </td> 
            <td> 
                @*@Html.ActionLink("Edit", "Edit", new { id=item.Id }) | 
                    @Html.ActionLink("Details", "Details", new { id=item.Id }) | 
                    @Html.ActionLink("Delete", "Delete", new { id=item.Id })*@ 
 
                <a href="javascript:void(0);" class="anchorDetail"  data-id="@item.Id">Details</a> 
 
            </td> 
        </tr> 
    } 
 
</table>  

As we can see we have detail anchor, with class anchorDetail and with data-id, which will get the id of clicked anchor and show the corresponding data to modal (detail view) on screen.

We have an Action method Details(int id) which will return the partial view.
public ActionResult Details(int Id) 

    FriendsInfo frnds = new FriendsInfo(); 
    frnds = db.FriendsInfo.Find(Id); 
    return PartialView("_Details",frnds); 
 

Here we added a partial view for this purpose to show detail view when user click on detail anchor in the list.

View Code
@model CodeFirst.Models.FriendsInfo 
 
<div> 
   
    <div class="modal-header"> 
        <button type="button" class="close" data-dismiss="modal" aria-hidden="true">×</button> 
        <h4 class="modal-title" id="myModalLabel">FriendsInfo</h4> 
    </div>                
                 
     
    <hr /> 
    <dl class="dl-horizontal"> 
        <dt> 
            @Html.DisplayNameFor(model => model.Name) 
        </dt> 
 
        <dd> 
            @Html.DisplayFor(model => model.Name) 
        </dd> 
 
        <dt> 
            @Html.DisplayNameFor(model => model.Mobile) 
        </dt> 
 
        <dd> 
            @Html.DisplayFor(model => model.Mobile) 
        </dd> 
 
        <dt> 
            @Html.DisplayNameFor(model => model.Address) 
        </dt> 
 
        <dd> 
            @Html.DisplayFor(model => model.Address) 
        </dd> 
 
    </dl> 
</div> 


We have a div for modal pop-up.

<div id='myModal' class='modal'> 
    <div class="modal-dialog"> 
        <div class="modal-content"> 
            <div id='myModalContent'></div> 
        </div> 
    </div>  
     
</div>  


Here is the script for showing modal (partial view) on above div when user click on detail anchor. Here we used Ajax call for this purpose.

Script
@section scripts 

    <script src="~/Scripts/jquery-1.10.2.min.js"></script> 
    <script src="~/Scripts/bootstrap.js"></script> 
    <script src="~/Scripts/bootstrap.min.js"></script> 
<script> 
    var TeamDetailPostBackURL = '/Home/Details'; 
    $(function () { 
        $(".anchorDetail").click(function () { 
            debugger; 
            var $buttonClicked = $(this); 
            var id = $buttonClicked.attr('data-id'); 
            var options = { "backdrop": "static", keyboard: true }; 
            $.ajax({ 
                type: "GET", 
                url: TeamDetailPostBackURL, 
                contentType: "application/json; charset=utf-8", 
                data: { "Id": id }, 
                datatype: "json", 
                success: function (data) { 
                    debugger; 
                    $('#myModalContent').html(data); 
                    $('#myModal').modal(options); 
                    $('#myModal').modal('show');                   
 
                }, 
                error: function () { 
                    alert("Dynamic content load failed."); 
                } 
            }); 
        }); 
        //$("#closebtn").on('click',function(){ 
        //    $('#myModal').modal('hide');   
 
        $("#closbtn").click(function () { 
            $('#myModal').modal('hide'); 
        });       
    }); 
    
</script> 
 

HostForLIFE.eu ASP.NET MVC 6 Hosting
HostForLIFE.eu is European Windows Hosting Provider which focuses on Windows Platform only. We deliver on-demand hosting solutions including Shared hosting, Reseller Hosting, Cloud Hosting, Dedicated Servers, and IT as a Service for companies of all sizes. We have customers from around the globe, spread across every continent. We serve the hosting needs of the business and professional, government and nonprofit, entertainment and personal use market segments.



European ASP.NET Core Hosting - HostForLIFE.eu :: Multiple Models in Single View in MVC

clock February 7, 2020 10:31 by author Peter

In MVC we cannot pass multiple models from a controller to the single view. This article provides a workaround for multiple models in a single view in MVC.

Problem Statement

Suppose I have two models, Teacher and Student, and I need to display a list of teachers and students within a single view. How can we do this?

The following are the model definitions for the Teacher and Student classes.

public class Teacher  
{  
    public int TeacherId { get; set; }  
    public string Code { get; set; }  
    public string Name { get; set; }  
}   
  
public class Student  
{  
    public int StudentId { get; set; }  
    public string Code { get; set; }  
    public string Name { get; set; }  
    public string EnrollmentNo { get; set; }  
}  

The following are the methods that help us to get all the teachers and students.

private List<Teacher> GetTeachers()  
{  
    List<Teacher> teachers = new List<Teacher>();  
    teachers.Add(new Teacher { TeacherId = 1, Code = "TT", Name = "Peter" });  
    teachers.Add(new Teacher { TeacherId = 2, Code = "JT", Name = "Scott" });  
    teachers.Add(new Teacher { TeacherId = 3, Code = "RT", Name = "Paul" });  
    return teachers;  
}   
  
public List<Student> GetStudents()  
{  
    List<Student> students = new List<Student>();  
    students.Add(new Student { StudentId = 1, Code = "L0001", Name = "Thomas", EnrollmentNo = "201404150001" });  
    students.Add(new Student { StudentId = 2, Code = "L0002", Name = "Brian", EnrollmentNo = "201404150002" });  
    students.Add(new Student { StudentId = 3, Code = "L0003", Name = "Chester", EnrollmentNo = "201404150003" });  
    return students;  
}  

There are many ways to use multiple models with a single view. Here I will explain ways one by one.

1. Using Dynamic Model

ExpandoObject (the System.Dynamic namespace) is a class that was added to the .Net Framework 4.0 that allows us to dynamically add and remove properties onto an object at runtime. Using this ExpandoObject, we can create a new object and can add our list of teachers and students into it as a property. We can pass this dynamically created object to the view and render list of the teacher and student.

Controller Code

public class HomeController : Controller  
{  
    public ActionResult Index()  
    {  
        ViewBag.Message = "Welcome to my demo!";  
        dynamic mymodel = new ExpandoObject();  
        mymodel.Teachers = GetTeachers();  
        mymodel.Students = GetStudents();  
        return View(mymodel);  
    }  
}  

We can define our model as dynamic (not a strongly typed model) using the @model dynamic keyword.

View Code

@using MultipleModelInOneView;  
@model dynamic  
@{  
    ViewBag.Title = "Home Page";  
}  
<h2>@ViewBag.Message</h2>  
   
<p><b>Teacher List</b></p>  
   
<table>  
    <tr>  
        <th>Id</th>  
        <th>Code</th>  
        <th>Name</th>  
    </tr>  
    @foreach (Teacher teacher in Model.Teachers)  
    {  
        <tr>  
            <td>@teacher.TeacherId</td>  
            <td>@teacher.Code</td>  
            <td>@teacher.Name</td>  
        </tr>  
    }  
</table>  
   
<p><b>Student List</b></p>  
   
<table>  
    <tr>  
        <th>Id</th>  
        <th>Code</th>  
        <th>Name</th>  
        <th>Enrollment No</th>  
    </tr>  
    @foreach (Student student in Model.Students)  
    {  
        <tr>  
            <td>@student.StudentId</td>  
            <td>@student.Code</td>  
            <td>@student.Name</td>  
            <td>@student.EnrollmentNo</td>  
        </tr>  
    }  
</table>  

2. Using View Model

ViewModel is nothing but a single class that may have multiple models. It contains multiple models as a property. It should not contain any method. In the above example, we have the required View model with two properties. This ViewModel is passed to the view as a model. To get intellisense in the view, we need to define a strongly typed view.

public class ViewModel  
{  
    public IEnumerable<Teacher> Teachers { get; set; }  
    public IEnumerable<Student> Students { get; set; }  
}  

Controller code

public ActionResult IndexViewModel()  
{  
    ViewBag.Message = "Welcome to my demo!";  
    ViewModel mymodel = new ViewModel();  
    mymodel.Teachers = GetTeachers();  
    mymodel.Students = GetStudents();  
    return View(mymodel);  
}  

View code

@using MultipleModelInOneView;  
@model ViewModel   
@{  
    ViewBag.Title = "Home Page";  
}  
<h2>@ViewBag.Message</h2>  
   
<p><b>Teacher List</b></p>  
   
<table>  
    <tr>  
        <th>Id</th>  
        <th>Code</th>  
        <th>Name</th>  
    </tr>  
    @foreach (Teacher teacher in Model.Teachers)  
    {  
        <tr>  
            <td>@teacher.TeacherId</td>  
            <td>@teacher.Code</td>  
            <td>@teacher.Name</td>  
        </tr>  
    }  
</table>  
   
<p><b>Student List</b></p>  
   
<table>  
    <tr>  
        <th>Id</th>  
        <th>Code</th>  
        <th>Name</th>  
        <th>Enrollment No</th>  
    </tr>  
    @foreach (Student student in Model.Students)  
    {  
        <tr>  
            <td>@student.StudentId</td>  
            <td>@student.Code</td>  
            <td>@student.Name</td>  
            <td>@student.EnrollmentNo</td>  
        </tr>  
    }  
</table>  

3. Using ViewData
ViewData is used to transfer data from the controller to the view. ViewData is a dictionary object that may be accessible using a string as the key. Using ViewData, we can pass any object from the controller to the view. The Type Conversion code is required when enumerating in the view.
For the preceding example, we need to create ViewData to pass a list of teachers and students from the controller to the view.

Controller Code
public
 ActionResult IndexViewData()  

{  
    ViewBag.Message = "Welcome to my demo!";  
    ViewData["Teachers"] = GetTeachers();  
    ViewData["Students"] = GetStudents();  
    return View();  
}  

View Code

@using MultipleModelInOneView;  
@{  
    ViewBag.Title = "Home Page";  
}  
<h2>@ViewBag.Message</h2>  
 <p><b>Teacher List</b></p>   
@{  
  
   IEnumerable<Teacher> teachers = ViewData["Teachers"] as IEnumerable<Teacher>;  
   IEnumerable<Student> students = ViewData["Students"] as IEnumerable<Student>;  
}  
<table>  
    <tr>  
        <th>Id</th>  
        <th>Code</th>  
        <th>Name</th>  
    </tr>  
    @foreach (Teacher teacher in teachers)  
    {  
        <tr>  
            <td>@teacher.TeacherId</td>  
            <td>@teacher.Code</td>  
            <td>@teacher.Name</td>  
        </tr>  
    }  
</table>  
 <p><b>Student List</b></p>  
<table>  
    <tr>  
        <th>Id</th>  
        <th>Code</th>  
        <th>Name</th>  
        <th>Enrollment No</th>  
    </tr>  
    @foreach (Student student in students)  
    {  
        <tr>  
            <td>@student.StudentId</td>  
            <td>@student.Code</td>  
            <td>@student.Name</td>  
            <td>@student.EnrollmentNo</td>  
        </tr>  
    }  
</table>  

4. Using ViewBag
ViewBag is similar to ViewData and is also used to transfer data from the controller to the view. ViewBag is a dynamic property. ViewBag is just a wrapper around the ViewData.

Controller Code

public ActionResult IndexViewBag()  
{  
    ViewBag.Message = "Welcome to my demo!";  
    ViewBag.Teachers = GetTeachers();  
    ViewBag.Students = GetStudents();  
    return View();  
}  

View Code

@using MultipleModelInOneView;  
@{  
    ViewBag.Title = "Home Page";  
}  
<h2>@ViewBag.Message</h2>  
   
<p><b>Teacher List</b></p>  
   
<table>  
    <tr>  
        <th>Id</th>  
        <th>Code</th>  
        <th>Name</th>  
    </tr>  
    @foreach (Teacher teacher in ViewBag.Teachers)  
    {  
        <tr>  
            <td>@teacher.TeacherId</td>  
            <td>@teacher.Code</td>  
            <td>@teacher.Name</td>  
        </tr>  
    }  
</table>  
   
<p><b>Student List</b></p>  
   
<table>  
    <tr>  
        <th>Id</th>  
        <th>Code</th>  
        <th>Name</th>  
        <th>Enrollment No</th>  
    </tr>  
    @foreach (Student student in ViewBag.Students)  
    {  
        <tr>  
            <td>@student.StudentId</td>  
            <td>@student.Code</td>  
            <td>@student.Name</td>  
            <td>@student.EnrollmentNo</td>  
        </tr>  
    }  
</table> 

5. Using Tuple

A Tuple object is an immutable, fixed-size and ordered sequence object. It is a data structure that has a specific number and sequence of elements. The .NET framework supports tuples up to seven elements. Using this tuple object we can pass multiple models from the controller to the view.

Controller Code

public ActionResult IndexTuple() 
{  
    ViewBag.Message = "Welcome to my demo!";  
    var tupleModel = new Tuple<List<Teacher>, List<Student>>(GetTeachers(), GetStudents());  
    return View(tupleModel);  
}  

View Code

@using MultipleModelInOneView;  
@model Tuple <List<Teacher>, List <Student>>  
@{  
    ViewBag.Title = "Home Page";  
}  
<h2>@ViewBag.Message</h2>   
<p><b>Teacher List</b></p>  
<table>  
    <tr>  
        <th>Id</th>  
        <th>Code</th>  
        <th>Name</th>  
    </tr>  
    @foreach (Teacher teacher in Model.Item1)  
    {  
        <tr>  
            <td>@teacher.TeacherId</td>  
            <td>@teacher.Code</td>  
            <td>@teacher.Name</td>  
        </tr>  
    }  
</table>  
<p><b>Student List</b></p>  
<table>  
    <tr>  
        <th>Id</th>  
        <th>Code</th>  
        <th>Name</th>  
        <th>Enrollment No</th>  
    </tr>  
    @foreach (Student student in Model.Item2)  
    {  
        <tr>  
            <td>@student.StudentId</td>  
            <td>@student.Code</td>  
            <td>@student.Name</td>  
            <td>@student.EnrollmentNo</td>  
        </tr>  
    }  
</table>  

6. Using Render Action Method
A Partial View defines or renders a partial view within a view. We can render some part of a view by calling a controller action method using the Html.RenderAction method. The RenderAction method is very useful when we want to display data in the partial view. The disadvantages of this method is that there are only multiple calls of the controller.


In the following example, I have created a view (named partialView.cshtml) and within this view I called the html.RenderAction method to render the teacher and student list.

Controller Code

public ActionResult PartialView()  
{  
    ViewBag.Message = "Welcome to my demo!";  
    return View();  
}  
   
/// <summary>  
/// Render Teacher List  
/// </summary>  
/// <returns></returns>  
public PartialViewResult RenderTeacher()  
{  
    return PartialView(GetTeachers());  
}  
   
/// <summary>  
/// Render Student List  
/// </summary>  
/// <returns></returns>  
public PartialViewResult RenderStudent()  
{  
    return PartialView(GetStudents());  
 

View Code

@{ 
   ViewBag.Title = "PartialView";  
<h2>@ViewBag.Message</h2>  
<div>  
    @{  
        Html.RenderAction("RenderTeacher");  
        Html.RenderAction("RenderStudent");  
    }  
</div>  

RenderTeacher.cshtml

@using MultipleModelInOneView;  
@model IEnumerable<MultipleModelInOneView.Teacher>  
 <p><b>Teacher List</b></p>  
<table>  
    <tr>  
        <th>Id</th>  
        <th>Code</th>  
        <th>Name</th>  
    </tr>  
    @foreach (Teacher teacher in Model)  
    {  
        <tr>  
            <td>@teacher.TeacherId</td>  
            <td>@teacher.Code</td>  
            <td>@teacher.Name</td>  
        </tr>  
    }  
  1. </table>  

RenderStudent.cshtml

@using MultipleModelInOneView;  
@model IEnumerable<MultipleModelInOneView.Student>   
  
<p><b>Student List</b></p>  
<table>  
    <tr>  
        <th>Id</th>  
        <th>Code</th>  
        <th>Name</th>  
        <th>Enrollment No</th>  
    </tr>  
    @foreach (Student student in Model)  
    {  
        <tr>  
            <td>@student.StudentId</td>  
            <td>@student.Code</td>  
            <td>@student.Name</td>  
            <td>@student.EnrollmentNo</td>  
        </tr>  
    }  
</table> 

Conclusion

This article helps us to learn how to pass multiple models from the controller to the view. I hope this will be helpful for beginners.



European ASP.NET Core Hosting - HostForLIFE.eu :: Know Further About ASP.NET Core Endpoint Routing

clock January 29, 2020 08:49 by author Scott

Introduction

In this post I will explain the new Endpoint Routing feature that has been added to the ASP.NET Core middleware pipeline starting with version 2.2 and how it is evolving through to the upcoming version 3.0 that is at preview 3 at present time.

The motivation behind endpoint routing

Prior to endpoint routing the routing resolution for an ASP.NET Core application was done in the ASP.NET Core MVC middleware at the end of the HTTP request processing pipeline. This meant that route information, such as what controller action would be executed, was not available to middleware that processed the request before the MVC middleware in the middleware pipeline.

It is particularly useful to have this route information available for example in a CORS or authorization middleware to use the information as a factor in the authorization process.

Endpoint routing also allows us to decouple the route matching logic from the MVC middleware, moving it into its own middleware. It allows the MVC middleware to focus on its responsibility of dispatching the request to the particular controller action method that is resolved by the endpoint routing middleware.

The new Endpoint Routing middleware

Due to the above mentioned reasons, the endpoint routing feature was born to allow the route resolution to happen earlier in the pipeline in a separate endpoint routing middleware. This new middleware can be placed at any point in the pipeline after which other middleware in the pipeline can access the resolved route data.

The endpoint routing middleware API is evolving with the upcoming 3.0 version of the .NET Core framework. For that reason, the API that I will describe in the following sections may not be the final version of the feature. However the over all concept and understanding of how route resolution and dispatch work using endpoint routing should still apply.

In the following sections I will walk you through the current iterations of endpoint routing implementation from version 2.2 to version 3.0 preview 3, then I will note some changes that are coming based on the current ASP.NET Core source code.

The three core concepts involved in Endpoint Routing

There are three overall concepts that you need to understand to be able to understand how endpoint routing works.

These are the following:

  • Endpoint route resolution
  • Endpoint dispatch
  • Endpoint route mapping

Endpoint route resolution

The endpoint route resolution is the concept of looking at the incoming request and mapping the request to an endpoint using route mappings. An endpoint represents the controller action that the incoming request resolves to, along with other metadata attached to the route that matches the request.

The job of the route resolution middleware is to construct and Endpoint object using the route information from the route that it resolves based on the route mappings. The middleware then places that object into the http context where other middleware the come after the endpoint routing middleware in the pipeline can access the endpoint object and use the route information within.

Prior to endpoint routing, route resolution was done in the MVC middleware at the end of the middleware pipeline. The current 2.2 version of the framework adds a new endpoint route resolution middleware that can be placed at any point in the pipeline, but keeps the endpoint dispatch in the MVC middleware. This will change in the 3.0 version where the endpoint dispatch will happen in a separate endpoint dispatch middleware that will replace the MVC middleware.

Endpoint dispatch

Endpoint dispatch is the process of invoking the controller action method that corresponds to the endpoint that was resolved by the endpoint routing middleware.

The endpoint dispatch middleware is the last middleware in the pipeline that grabs the endpoint object from the http context and dispatches to particular controller action that the resolved endpoint specifies.

Currently in version 2.2 dispatching to the action method is done in the MVC middleware at the end of the pipeline.

In the version 3.0 preview 3, the MVC middleware is removed. Instead the endpoint dispatch happens at the end of the middleware pipeline by default. Because the MVC middleware is removed, the route map configuration that is usually passed to the MVC middleware, is instead passed to the endpoint route resolution middleware.

Based on the current source code, the upcoming 3.0 final release should have a new endpoint routing middleware that is placed at the end of the pipeline to make the endpoint dispatch explicit again. The route map configuration will be passed to this new middleware instead of the endpoint route resolution middleware as it is in version 3 preview 3.

Endpoint route mapping

When we define route middleware we can optionally pass in a lambda function that contains route mappings that override the default route mapping that ASP.NET Core MVC middleware extension method specifies.

Route mappings are used by the route resolution process to match the incoming request parameters to a route specified in the rout map.

With the new endpoint routing feature the ASP.NET Core team had to decide which middleware, the endpoint resolution or the endpoint dispatch middleware, should get the route mapping configuration lambda as a parameter.

In fact this is the part of the endpoint routing where the API is in flux. As I write this post, the route mapping is being moved from the route resolution middleware to the endpoint dispatcher middleware.

I will show you the route mapping API in version 3 preview 3 first, then show you the latest route mapping API in the ASP.NET Core source code. In the source code version, we will see that the route mapping is moved to the endpoint dispatcher middleware extension method.

Its important to note that the endpoint resolution happens during runtime request handling after the route mapping is setup during application startup configuration. Therefor the route resolution middleware has access to the route mappings during request handling regardless of which middleware the route map configuration is passed to. 

Accessing the resolved endpoint

Any Middleware after the endpoint route resolution middleware will be able to access the resolved endpoint through the HttpContext.

The following code snippet shows how this can be done in your own middleware:

//our custom middleware
app.Use((context, next) =>
{
    var endpointFeature = context.Features[typeof(Microsoft.AspNetCore.Http.Features.IEndpointFeature)]
                                           as Microsoft.AspNetCore.Http.Features.IEndpointFeature;

    Microsoft.AspNetCore.Http.Endpoint endpoint = endpointFeature?.Endpoint;

    //Note: endpoint will be null, if there was no
    //route match found for the request by the endpoint route resolver middleware
    if (endpoint != null)
    {
        var routePattern = (endpoint as Microsoft.AspNetCore.Routing.RouteEndpoint)?.RoutePattern
                                                                                   ?.RawText;

        Console.WriteLine("Name: " + endpoint.DisplayName);
        Console.WriteLine($"Route Pattern: {routePattern}");
        Console.WriteLine("Metadata Types: " + string.Join(", ", endpoint.Metadata));
    }
    return next();
});

As you can see I am accessing the resolved endpoint object through the IEndpointFeature or the Http Context. The framework provides wrapper methods to access the endpoint object without having to reach directly into the context as I have shown here.

Endpoint routing configuration

The middleware pipeline endpoint route resolver middleware, endpoint dispatcher middleware and endpoint route mapping lambda is setup in the Startup.Configure method of the Startup.cs file of ASP.NET Core project.

This configuration changed between 2.2 and 3.0 preview 3 versions and is still changing before the 3.0 release version. So in order to demonstrate the endpoint routing configuration I am going to declare the general form of the endpoint routing middleware configuration as pseudo code based on the three core concepts listed above:

//psuedocode that passes route map to endpoint resolver middleware
public void Configure(IApplicationBuilder app
                     , IHostingEnvironment env)
{
    //middleware configured before the UseEndpointRouteResolverMiddleware middleware
    //that does not have access to the endpoint object
    app.UseBeforeEndpointResolutionMiddleware();

    //middleware that inspects the incoming request, resolves a match to the route map
    //and stores the resolved endpoint object into the httpcontext
    app.UseEndpointRouteResolverMiddleware(routes =>
    {
        //This is the route mapping configuration passed to the endpoint resolver middleware
        routes.MapControllers();
    })

    //middleware after configured after the UseEndpointRouteResolverMiddleware middleware
    //that can access to the endpoint object
    app.UseAfterEndpointResolutionMiddleware();

    //The middleware at the end of the pipeline that dispatches the controler action method
    //will replace the current MVC middleware
    app.UseEndpointDispatcherMiddleware();
}

This version of our pseudo code shows the route mappings lambda passed as a parameter to the UseEndpointRouteResolverMiddleware endpoint route resolution middleware extension method.

An alternate version that matches what the current source code looks like, is shown below:

//psuedocode version 2 that passes route map to endpoint dispatch middleware
public void Configure(IApplicationBuilder app
                     , IHostingEnvironment env)
{
    app.UseBeforeEndpointResolutionMiddleware()

    //This is the endpoint route resolver middleware
    app.UseEndpointRouteResolverMiddleware();

    //This middleware can access the resolved endpoint object via HttpContext
    app.UseAfterEndpointResolutionMiddleware();

    //This is the endpoint dispatch middleware
    app.UseEndpointDispatcherMiddleware(routes =>
    {
        //This is the route mapping configuration passed to the endpoint dispatch middleware
        routes.MapControllers();
    });
}

In this version the route mapping configuration is passed as a parameter to the endpoint dispatch middleware extension method UseEndpointDispatcherMiddleware.

Either way the UseEndpointRouteResolverMiddleware() endpoint resolver middleware will have access to the route mappings at request handling time to do the route matching.

Once the route is matched by UseEndpointRouteResolverMiddleware an Endpoint object will be constructed with the route parameters and set to the httpcontext so that the middleware in the pipeline that follow, can access the Endpoint object and use it if needed.

In version 3 preview 3 version of this pseudo code, the route mapping is passed to UseEndpointRouteResolverMiddleware and there does not exist a UseEndpointDispatcherMiddleware at the end of the pipeline. This is because in this version the ASP.NET framework itself implicitly dispatches the resolved endpoint at the end of the request pipeline.

So the pseudo code representing version 3 preview 3 has the form below:

//pseudo code representing v3 preview 3 endpoint routing API
public void Configure(IApplicationBuilder app
                     , IHostingEnvironment env)
{
    app.UseBeforeEndpointResolutionMiddleware()

    //This is the endpoint route resolver middleware
    app.UseEndpointRouteResolverMiddleware(routes =>
    {
        //The route mapping configuration is passed to the endpoint resolution middleware
        routes.MapControllers();
    })

    //This middleware can access the resolved endpoint object via HttpContext
    app.UseAfterEndpointResolutionMiddleware()

    // The resolved endpoint is implicitly dispatched here at the end of the pipeline
    // and so there is no explicit call to a UseEndpointDispatcherMiddleware
}

This API looks to be changing with the 3.0 release version, as the current source code shows that the UseEndpointDispatcherMiddleware is added back in and it is the middleware that takes the route mappings as a parameter as illustrated by the second version of the pseudo code above.

Endpoint routing in version 2.2

If you create a Web API project using version 2.2 of the .NET Core SDK you will see the following code in the Startup.Configure method:

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    if (env.IsDevelopment())
        app.UseDeveloperExceptionPage();
    else
        app.UseHsts();

    app.UseHttpsRedirection();

    //By default endpoint routing is not added
    //the MVC middleware dispatches the controller action
    //and the MVC middleware configures the default route mapping
    app.UseMvc();
}

The MVC middleware is configured at the end of the middleware pipeline using the UseMvc() extension method. This method internally sets the default MVC route mapping configuration at startup configuration time and dispatches the controller action during request handling.

By default the out of the box template in v2.2 just configures the MVC dispatcher middleware. As such the MVC middleware also handles the route resolution based on the route map configuration and the incoming request data.

However we can add Endpoint Routing using some additional configuration as shown below:

using Microsoft.AspNetCore.Internal;

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    if (env.IsDevelopment())
        app.UseDeveloperExceptionPage();
    else
        app.UseHsts();

    //added endpoint routing that will resolve the endpoint object
    app.UseEndpointRouting();

    //middleware below will have access to the Endpoint

    app.UseHttpsRedirection();

    //the MVC middleware dispatches the controller action
    //and the MVC middleware configures the default route mapping
    app.UseMvc();
}

Here we have added the namespace Microsoft.AspNetCore.Internal. Including it, enables an additional IApplicationBuilder extension method UseEndpointRouting that is the endpoint resolution middleware that resolves the route and adds the Endpoint object to the httpcontext.

You can check out the source code for UseEndpointRouting extension method in version 2.2 at:

https://github.com/aspnet/AspNetCore/blob/v2.2.4/src/Http/Routing/src/Internal/EndpointRoutingApplicationBuilderExtensions.cs

In version 2.2 the MVC middleware at the end of the pipeline acts as the endpoint dispatcher middleware. It will dispatch the resolved endpoint to the proper controller action.

The endpoint resolution middleware uses the route mappings configured by the MVC middleware.

Once we have enabled endpoint routing we can actually inspect the resolved endpoint object if we add our own custom middleware show below:

using Microsoft.AspNetCore.Http.Features;
using Microsoft.AspNetCore.Routing;

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    if (env.IsDevelopment())
        app.UseDeveloperExceptionPage();
    else
        app.UseHsts();

    app.UseEndpointRouting();

    app.UseHttpsRedirection();

    //our custom middlware
    app.Use((context, next) =>
    {
        var endpointFeature = context.Features[typeof(IEndpointFeature)] as IEndpointFeature;
        var endpoint = endpointFeature?.Endpoint;

        //note: endpoint will be null, if there was no resolved route
        if (endpoint != null)
        {
            var routePattern = (endpoint as RouteEndpoint)?.RoutePattern
                                                          ?.RawText;

            Console.WriteLine("Name: " + endpoint.DisplayName);
            Console.WriteLine($"Route Pattern: {routePattern}");
            Console.WriteLine("Metadata Types: " + string.Join(", ", endpoint.Metadata));
        }
        return next();
    });

    app.UseMvc();
}

As you can see we can inspect and print out the endpoint object that the endpoint routing resolution middleware UseEndpointRouting has resolved. The endpoint object will be null, if the resolver was not able to match the request to a mapped route. We needed to pull in two additional namespaces to access the endpoint routing features.

Endpoint routing in Version 3 preview 3

In version 3 preview 3, endpoint routing will become a full fledged citizen of ASP.NET Core and we will finally have separation between the MVC controller action dispatcher and the route resolution middleware.

Here is the endpoint startup configuration in version 3 preview 3.

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    if (env.IsDevelopment())
        app.UseDeveloperExceptionPage();
    else
        app.UseHsts();

    app.UseHttpsRedirection();

    app.UseRouting(routes =>
    {
        routes.MapControllers();
    });

    app.UseAuthorization();

    //No need to have a dispatcher middleware here.
    //The resolved endpoint is automatically dispatched to a controller action at the end
    //of the middleware pipeline
    //If an endpoint was not able to be resolved, a 404 not found is returned at the end
    //of the middleware pipeline
}

As you can see we have a app.UseRouting() method that configures the endpoint route resolution middleware. The method also takes a anonymous lambda function that configures the route mappings that the route resolver middleware will use to resolve the incoming request endpoint.

The routes.MapControllers() inside the mapping function configures the default MVC routes.

You will also notice that there is a app.UseAuthorization() after app.UseRouting() which configures the authorization middleware. This middleware will have access the httpcontext endpoint object set by the endpoint routing middleware.

Notice that we don’t have any MVC or endpoint dispatch middleware configured at the end of the method, after all other middleware configuration.

This is because the behavior of the version 3 preview 3 build is that the resolved endpoint will be implicitly dispatched to the controller action by the framework itself.

Similar to what we did for version 2.2 we can add the same custom middleware to inspect the resolved endpoint object.

using Microsoft.AspNetCore.Http.Features;
using Microsoft.AspNetCore.Routing;

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    if (env.IsDevelopment())
        app.UseDeveloperExceptionPage();
    else
        app.UseHsts();

    app.UseHttpsRedirection();

    app.UseRouting(routes =>
    {
        routes.MapControllers();
    });

    app.UseAuthorization();

    //our custom middleware
    app.Use((context, next) =>
    {
        var endpointFeature = context.Features[typeof(IEndpointFeature)] as IEndpointFeature;
        var endpoint = endpointFeature?.Endpoint;

        //note: endpoint will be null, if there was no
        //route match found for the request by the endpoint route resolver middleware
        if (endpoint != null)
        {
            var routePattern = (endpoint as RouteEndpoint)?.RoutePattern
                                                          ?.RawText;

            Console.WriteLine("Name: " + endpoint.DisplayName);
            Console.WriteLine($"Route Pattern: {routePattern}");
            Console.WriteLine("Metadata Types: " + string.Join(", ", endpoint.Metadata));
        }
        return next();
    });

    //the endpoint is dispatched by default at the end of the middleware pipeline
}

Endpoint routing in upcoming ASP.NET Core version 3.0 source code repository

As we approach the version 3.0 release of the framework, it looks like the team is trying to make endpoint routing more explicit by adding back in the call to endpoint dispatcher middleware configuration. They are also moving back the route mapping configuration option to the dispatcher middleware configuration method.

We can see how this is changed yet again by peeking at the current source code.

Here is a snippet from the source code for the version 3.0 sample application music store at:

https://github.com/aspnet/AspNetCore/blob/master/src/MusicStore/samples/MusicStore/Startup.cs

public void Configure(IApplicationBuilder app)
{
    // Configure Session.
    app.UseSession();

    // Add static files to the request pipeline
    app.UseStaticFiles();

    // Add the endpoint routing matcher middleware to the request pipeline
    app.UseRouting();

    // Add cookie-based authentication to the request pipeline
    app.UseAuthentication();

    // Add the authorization middleware to the request pipeline
    app.UseAuthorization();

    // Add endpoints to the request pipeline
    app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllerRoute(
            name: "areaRoute",
            pattern: "{area:exists}/{controller}/{action}",
            defaults: new { action = "Index" });

        endpoints.MapControllerRoute(
            name: "default",
            pattern: "{controller}/{action}/{id?}",
            defaults: new { controller = "Home", action = "Index" });

        endpoints.MapControllerRoute(
            name: "api",
            pattern: "{controller}/{id?}");
    });
}

As you can see that we have something similar to my pseudo code implementation that I detailed above.

Particularly, we still have the app.UseRouting() middleware setup from the version 3 preview 3, but now we also have an explicit app.UseEndpoints() endpoint dispatch method that more aptly named for what it does.

The UseEndpoints is a new IApplicationBuilder extension method that provides the endpoint dispatch implementation.

You can check out the source code for the UseEndpoints and UseRouting methods here:

https://github.com/aspnet/AspNetCore/blob/master/src/Http/Routing/src/Builder/EndpointRoutingApplicationBuilderExtensions.cs

Also note that the route mapping configuration lambda have been moved from the UseRouting middleware to the new UseEndpoints middleware.

The UseRouting endpoint route resolver will still have access to the mappings to resolve the endpoint at request handling time. Even though they are passed to the UseEndpoints middleware during startup configuration.

Adding Endpoint routing middleware to the DI container

To use endpoint routing, we also need to add the middleware to the DI container in the Startup.ConfigureServices method.

ConfigureServices in Version 2.2

For version 2.2 of the framework we need to explicitly add the call to services.AddRouting() method shown below to add the endpoint routing feature to the DI container:

public void ConfigureServices(IServiceCollection services)
{
    services.AddRouting()

    services.AddMvc()
            .SetCompatibilityVersion(CompatibilityVersion.Version_2_2);
}

ConfigureServices in Version 3 preview 3

For version 3 preview 3 build of the framework, endpoint routing already comes configured in the DI container under the covers in the AddMvc() extension method:

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc()
            .AddNewtonsoftJson();
}

Setting up Endpoint Authorization using endpoint routing and route mappings

When working with the version 3 preview 3 release we can attach authorization metadata to an endpoint. We do this using the route mappings configuration fluent API RequireAuthorization method.

The endpoint routing resolver will access this metadata when processing a request and add it to the Endpoint object that it sets on the httpcontext.

Any middleware in the pipeline after the route resolution middleware can access this authorization data by accessing the resolved Endpoint object.

In particular the authorization middleware can use this data to make authorization decisions.

Currently the route mapping configuration parameters are passed into the endpoint route resolver middleware, but as previously mentioned, in the future releases, the route mapping configuration will be passed into the endpoint dispatcher middleware.

Either way the attached authorization metadata will be available for the endpoint resolver middleware to use.

Below is an example of the version 3 preview 3 Startup.Configure method where I have added a new /secret route to the endpoint resolver middleware route map configuration lambda parameter:

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    if (env.IsDevelopment())
        app.UseDeveloperExceptionPage();
    else
        app.UseHsts();

    app.UseHttpsRedirection();

    app.UseRouting(routes =>
    {
        routes.MapControllers();

        //Mapped route that gets attached authorization metadata using the RequireAuthorization extension method.
        //This metadata will be added to the resolved endpoint for this route by the endpoint resolver
        //The app.UseAuthorization() middleware later in the pipeline will get the resolved endpoint
        //for the /secret route and use the authorization metadata attached to the endpoint
        routes.MapGet("/secret", context =>
        {
            return context.Response.WriteAsync("secret");
        }).RequireAuthorization(new AuthorizeAttribute(){ Roles = "admin" });
    });

    app.UseAuthentication();

    //the Authorization middleware check the resolved endpoint object
    //to see if it requires authorization. If it does as in the case of
    //the "/secret" route, then it will authorize the route, if it the user is in the admin role
    app.UseAuthorization();

    //the framework implicitly dispatches the endpoint at the end of the pipeline.
}

You can see that I am using the RequireAuthorization method to add an AuthorizeAttribute attribute to the /secret route. This route will then only be authorized to be dispatched for a user in the admin role, by the authorization middleware, that comes before the endpoint dispatch occurs.

As I showed for version 3.3 preview 3 that we can add middleware to inspect the resolved endpoint object in httpcontext so can we here to inspect the AuthorizeAttribute added to the endpoint metadata:

using Microsoft.AspNetCore.Http.Features;
using Microsoft.AspNetCore.Routing;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Authorization;

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    if (env.IsDevelopment())
        app.UseDeveloperExceptionPage();
    else
        app.UseHsts();

    app.UseHttpsRedirection();

    app.UseRouting(routes =>
    {
        routes.MapControllers();

        routes.MapGet("/secret", context =>
        {
            return context.Response.WriteAsync("secret");
        }).RequireAuthorization(new AuthorizeAttribute(){ Roles = "admin" });
    });

    app.UseAuthentication();

    //our custom middleware
    app.Use((context, next) =>
    {
        var endpointFeature = context.Features[typeof(IEndpointFeature)] as IEndpointFeature;
        var endpoint = endpointFeature?.Endpoint;

        //note: endpoint will be null, if there was no
        //route match found for the request by the endpoint route resolver middleware
        if (endpoint != null)
        {
            var routePattern = (endpoint as RouteEndpoint)?.RoutePattern
                                                          ?.RawText;

            Console.WriteLine("Name: " + endpoint.DisplayName);
            Console.WriteLine($"Route Pattern: {routePattern}");
            Console.WriteLine("Metadata Types: " + string.Join(", ", endpoint.Metadata));
        }
        return next();
    });

    app.UseAuthorization();

    //the framework implicitly dispatches the endpoint here.
}

This time I have added the custom middleware before the Authorization middleware and pulled in two additional namespaces.

Navigating to the /secret route and inspecting the metadata, you can see that it contains the Microsoft.AspNetCore.Authorization.AuthorizeAttribute type in addition to the Microsoft.AspNetCore.Routing.HttpMethodMetadata type.

References used for this article

The following articles contain source material that I used as a reference for this article:

https://devblogs.microsoft.com/aspnet/aspnet-core-3-preview-2/

Update for version 3 preview 4

Around the time I published this article, ASP.NET Core 3.0 preview 4 was released. It adds the changes that I described in the latest source code as can be seen in the code snippet from Startup.cs file below when creating a new webapi project:

//code from Startup.cs file in a webapi project template

using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Http;

public void ConfigureServices(IServiceCollection services)
{
    services.AddControllers()
            .AddNewtonsoftJson();
}

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    if (env.IsDevelopment())
        app.UseDeveloperExceptionPage();
    else
        app.UseHsts();

    app.UseHttpsRedirection();

    //add endpoint resolution middlware
    app.UseRouting();

    app.UseAuthorization();

    //add endpoint dispatch middleware
    app.UseEndpoints(endpoints =>
    {
        //route map configuration
        endpoints.MapControllers();

        //route map I added to show Authorization setup
        endpoints.MapGet("/secret", context =>
        {
            return context.Response.WriteAsync("secret");
        }).RequireAuthorization(new AuthorizeAttribute(){ Roles = "admin" }); 
    });
}

As you can see this version adds the explicit UseEndpoints middleware extension method at the end of the pipeline that adds the endpoint dispatch middleware. Also the route configuration parameter has been moved from the UseRouting method in preview 3 to the UseEndpoints in preview 4.

Conclusion

Endpoint routing allows ASP.NET Core applications to determine the endpoint that will be dispatched, early on in the middleware pipeline, so that later middleware can use that information to provide features not possible with the current pipeline configuration.

This makes the ASP.NET Core framework more flexible since it decouples the route matching and resolution functionality from the endpoint dispatching functionality, which until now was all bundled in with the MVC middleware.



ASP.NET MVC Hosting - HostForLIFE.eu :: Display Mode Provider in MVC 5 Application

clock January 22, 2020 10:19 by author Peter

This article will solve a problem. Display modes in ASP.NET MVC 5 provide a way of separating page content from the way it is rendered on various devices, like web, mobile, iPhone, iPod and Windows Phones. All you need to do is to define a display mode for each device, or class of devices.

First you create a model and context class. We create an Employee class that has the following properties like.
    public class Employee 
    { 
        public Guid ID { get; set; } 
        [Display(Name="First Name")] 
        public string FirstName { get; set; } 
        [Display(Name = "Last Name")] 
        public string LastName { get; set; } 
        [Display(Name = "Department")] 
        public string Department { get; set; } 
        [Display(Name = "Salary")] 
        public double Salary { get; set; } 
        [Display(Name = "Address")] 
        public string Address { get; set; } 
    }


And second is the context class like this that inherits the DbContext class.
    public class DBConnectionContext:DbContext 
    {         
       public DBConnectionContext(): base("name=dbContext") 
       { 
             Database.SetInitializer(new DropCreateDatabaseIfModelChanges 
             <DBConnectionContext>()); 
       } 
            public DbSet<Employee> Employees { get; set; } 
    }


If you want to recreate data every time the model changes, add these lines of code.
    Database.SetInitializer(new DropCreateDatabaseIfModelChanges<DbConnectionContext>());

You also have a web config file. We configure connectionStrings in the Web.Config file.
    <connectionStrings> 
    <add name="dbContext" connectionString="Data Source=localhost; Initial Catalog=CommonDataBase; Integrated Security=true"  
          providerName="System.Data.SqlClient" /> 
     </connectionStrings>


Then you create a controller class in a controller folder and edit the name as HomeController. Add a Scaffold to select a MVC 5 Controller with Views, using Entity Framework.

DisplayModes

DisplayModes give you another level of flexibility on top of the default capabilities we saw in the last section. DisplayModes can also be used along with the previous feature so we will simply build off of the site we just created. Let's say we wanted to show an alternate view for the Windows Phone 8, iPhone, iPod or Android.

Windows Phone 8 DisplayMode

Now that you have made the override files, you can use a DisplayMode to show them for the appropriate phones.

The best time to set this up is when the application starts. Here is our global.asax.cs, with the DisplayMode setup.
    DisplayModeProvider.Instance.Modes.Insert(1, new DefaultDisplayMode("WP") 
    { 
        ContextCondition = (ctx => ctx.GetOverriddenUserAgent() 
        .IndexOf("Windows Phone OS", StringComparison.OrdinalIgnoreCase) > 0)   
     }); 
      
    DisplayModeProvider.Instance.Modes.Insert(1, new DefaultDisplayMode("iPhone") 
    { 
        ContextCondition = (ctx => ctx.GetOverriddenUserAgent() 
        .IndexOf("iPhone", StringComparison.OrdinalIgnoreCase) > 0)   
    }); 
      
    DisplayModeProvider.Instance.Modes.Insert(1, new DefaultDisplayMode("Android") 
    { 
        ContextCondition = (ctx => ctx.GetOverriddenUserAgent() 
        .IndexOf("Android", StringComparison.OrdinalIgnoreCase) > 0)   
    }); 

The DisplayModeProvider Class
DisplayModeProvider holds a list of DefaultDisplayMode obejects, each representing display mode. And the provider holds the two display modes, default and mobile. The default display mode in an empty string and the second holds the mobile string.


We just create multiple View with [View].Android.cshtml, [View].iPhone.cshtml and so on for every device such as:

We create an index for iPhone and create a new employee in iPhone Index.iPhone.cshtml and Create.iPhone.cshtml.


We create an index for Windows Phone and create a new employee in the Windows Phone Index.WP.cshtml Create.WP.cshtml.


We create an index for Android and create a new employee in Windows Phone Index.Android.cshtml Create.Android.cshtml.



European ASP.NET Core Hosting :: Getting Started with Entity Framework Core

clock January 21, 2020 08:13 by author Scott

This walkthrough demonstrates the minimum required to create a database using Entity Framework Core in an ASP.NET Core application, and to develop basic CRUD screens. The walkthrough assumes that you have .Net Core SDK installed and that you have a suitable development environment/text editor. Visual Studio Code will be used in this example.

Creating an ASP.NET Core application link

If you have a version of Visual Studio that supports .Net Core (2015 or greater), you can use the project templates to create a new .Net Core Web application. Alternatively, you can use a command line tool to create and build the project. In this example, you will use the command line tool from within Visual Studio Code.

The first step is to create a folder for the application in a suitable location. Name the folder EFCoreWebDemo. Once created, open the folder in Visual Studio Code. Having done that, press Ctrl + ' to open a Terminal window.

Next, use the terminal to type these commands

dotnet new mvc 
dotnet add package Microsoft.EntityFrameworkCore.SqlServer
dotnet add package --version 1.1.0-msbuild3-final Microsoft.EntityFrameworkCore.Tools
dotnet restore     
dotnet run
         

The commands above

- scaffolds a starter ASP.NET Core application that uses the MVC framework

- adds the Entity FrameworkCore and EF Core tooling packages from Nuget to the project

- restores all packages

- builds and runs the application

You should get confirmation that the application is running on port 5000:

If you navigate to http://localhost:5000 in your preferred browser, you should see the standard Microsoft MVC application running:

To continue with the next steps, stop the application by pressing Ctrl + C.

Open the EFCoreDemo folder in Visual Studio Code.

Modify the .csproj file to include the following section:

<ItemGroup>
    <DotNetCliToolReference
        Include="Microsoft.EntityFrameworkCore.Tools.DotNet"
        Version="1.0.0-msbuild3-final" />
</ItemGroup>

This step is only necessary if the .csproj file wasn't automatically modified to add the entry when the Tools package was installed. See https://github.com/aspnet/EntityFramework/issues/7358.

Once you have made this amendment, you can test to see if ef commands are available to you by navigating to the project folder in a terminal/command window and typing the following command:

dotnet ef -h

This should result in the initial help for the EF tools being displayed:

Creating the Model

Add a folder named Model to the application.

Add a new file named EFCoreWebDemoContext.cs to the Model folder and add the following code to it:

using Microsoft.EntityFrameworkCore;

namespace EFCoreWebDemo
{
    public class EFCoreWebDemoContext : DbContext
    {
        public DbSet<Book> Books { get; set; }
        public DbSet<Author> Authors { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {         optionsBuilder.UseSqlServer(@"Server=.\;Database=EFCoreWebDemo;Trusted_Connection=True;MultipleActiveResultSets=true");
        }
    }
}

Note: The model, particularly the DbContext class, is declared inside a namespace. If you don't place your context class in a namespace, you may come up against this long running open bug when adding your migration.

Next, add a new file named Author.cs and add the following code to it:

using System.Collections.Generic;

namespace EFCoreWebDemo
{
    public class Author
    {
        public int AuthorId { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public ICollection<Book> Books { get; set; } = new List<Book>();
    }
}

Finally, add a new file named Book.cs and add the following code to it:

namespace EFCoreWebDemo
{
    public class Book
    {
        public int BookId { get; set; }
        public string Title { get; set; }
        public int AuthorId { get; set; }
        public Author Author { get; set; }
    }
}

This code defines classes for two entities - Book and Author that participate in a fully defined one-to-many relationship. The code also includes a class named EFCoreDemoContext that inherits from DbContext. This class has two DbSet properties that represent the tables in the database (which is yet to be created). The EFCoreWebDemoContext class also includes a method named OnConfiguring where the connection string for a SQL Server database is defined. You should change this to suit your environment and database provider.

Before moving on to the migration, type dotnet build to ensure that the application builds correctly.

Adding A Migration

Migrations are used to keep the database schema in sync with the model. There is no database at the moment, so the first migration will create it and add tables for the entities represented by the DbSet properties on the EFCoreDemoContext that you added.

Visual Studio Code doesn't provide any support (at the time of writing) for creating and executing migrations. Therefore they will be managed using the command prompt. Having opened one (if it's not still open from having created and built the application), navigate to the project folder and enter the following command:

dotnet ef  migrations add CreateDatabase

A new folder named Migrations is added to the project. It contains the code for the migration and a model snapshot.

Enter the following command to execute the migration:

dotnet ef database update

The database is created but all of the string fields are unlimited in size (nvarchar(MAX) in SQL Server).

Modifying The Database With Migrations

In the next section, you will modify the model to set limits to the size of selected string properties, and then use migrations to push those changes to the database schema.

Add the following to the using directives at the top of Author.cs and Book.cs:

using System.ComponentModel.DataAnnotations;

Modify the Book and Author entities so that they look like this:

public class Book
{
    public int BookId { get; set; }
    [StringLength(255)]
    public string Title { get; set; }
    public int AuthorId { get; set; }
    public Author Author { get; set; }
}

public class Author
{
    public int AuthorId { get; set; }
    [StringLength(50)]
    public string FirstName { get; set; }
    [StringLength(75)]
    public string LastName { get; set; }
    public ICollection<Book> Books { get; set; } = new List<Book>();
}

In the Terminal, type the following command:

dotnet ef migrations add LimitStrings

followed by

dotnet ef database update

This will scaffold a migration that will alter the size of the Book's Title field and the Author's FirstName and LastName fields. You should also get a warning that the scaffolded migration could lead to data loss. In this case, there is no data to be lost so the warning can be ignored.

Once the migration has been applied, the database schema will be altered. Here's how the modified Author table should look:

Working With Data

In the next section, you will create a web page for adding new authors to the database and for displaying them. Add a new file named AuthorController.cs to the Controllers folder. Add the following code to the newly created file:

using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;

namespace EFCoreWebDemo.Controllers
{
    public class AuthorController : Controller
    {
        public async Task<IActionResult> Index()
        {
            using (var context = new EFCoreWebDemoContext())
            {
                var model = await context.Authors.AsNoTracking().ToListAsync();
                return View(model);
            }           
        } 

        [HttpGet]
        public IActionResult Create()
        {
            return View();
        }

        [HttpPost]
        public async Task<IActionResult> Create([Bind("FirstName, LastName")] Author author)
        {
            using (var context = new EFCoreWebDemoContext())
            {
                context.Add(author);
                await context.SaveChangesAsync();
                return RedirectToAction("Index");
            }
        }
    }
}

The code in the Index method retrieves all authors from the database and passes them to the View. The AsNoTracking method is used to prevent the context from unnecessarily tracking the data because it is intended for read-only use. The DbContext is instantiated in a using block to ensure that it is disposed properly.

The Create method that takes an Author as a parameter is responsible for adding the new author to the database. It uses the approach whereby data is added directly to the DbContext, allowing the context to infer the type of data to be added to the database.

Finally, add a new folder to the Views folder and name it Author. Add new file to the new folder called Index.cshtml. Add the following code to it:

@model IEnumerable<Author>
@{
    ViewBag.Title = "Authors";
}
<h1>@ViewBag.Title</h1>
<ul>
@foreach (var author in Model)
{
    <li>@author.FirstName @author.LastName</li>
}
</ul>

<div>@Html.ActionLink("New", "create")

Then add a new file named Create.cshtml to the Author folder with the following code:

@model Author
@{
    ViewBag.Title = "New Author";
}

<h1>@ViewBag.Title</h1>

@using(Html.BeginForm()){
  <div class="form-group">
    @Html.LabelFor(model => model.FirstName)
    @Html.TextBoxFor(model => model.FirstName, new { @class="form-control"})
  </div>
  <div class="form-group">
    @Html.LabelFor(model => model.LastName)
    @Html.TextBoxFor(model => model.LastName, new { @class="form-control"})
  </div>
  <button type="submit" class="btn btn-default">Submit</button>
}

Run the application by typing the following command:

dotnet run

Open a browser and navigate to http://localhost:5000/author/create. You should see a data entry form similar to this:

 

Enter an author's name and submit the form. You should get redirected to the index page where a list of any authors entered so far is displayed:

 

Adding Related Data

In the next section, you will add new books to the database which will be related to an existing author.

First, add a new file to the Controllers folder named BookController.cs. Add the following code to the new file:

using System.Threading.Tasks;
using System.Linq;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using Microsoft.AspNetCore.Mvc.Rendering;

namespace EFCoreWebDemo.Controllers
{

    public class BookController : Controller
    {
        public async Task<IActionResult> Index()
        {
            using (var context = new EFCoreWebDemoContext())
            {
                var model = await context.Authors.Include(a => a.Books).AsNoTracking().ToListAsync();
                return View(model);
            }          
        } 

        [HttpGet]
        public async Task<IActionResult> Create()
        {
            using(var context = new EFCoreWebDemoContext())
            {
                var authors = await context.Authors.Select(a => new SelectListItem {
                    Value = a.AuthorId.ToString(),
                    Text = $"{a.FirstName} {a.LastName}"
                }).ToListAsync();
                ViewBag.Authors = authors;
            }
            return View();
        }

        [HttpPost]
        public async Task<IActionResult> Create([Bind("Title, AuthorId")] Book book)
        {
            using (var context = new EFCoreWebDemoContext())
            {
                context.Books.Add(book);
                await context.SaveChangesAsync();
                return RedirectToAction("Index");
            }
        }
    }
}

This time, the code in the Index method retrieves all authors and uses the Include method to eagerly load the related books from the database and passes them to the View. Again, the AsNoTracking method is used. The authors and their books only being used for display.

In the first Create method, each of the authors are retrieved from the database and projected into a new form - a SelectListItem. Non-entity types are not tracked by the context which is why the AsNoTracking method is not used in this case, despite the fact that the data is for read-only use.

The second Create method features an example of the entity being added to its DBSet, rather than the DbContext as was the case for the author.

Next, add a new folder to the Views folder named Book. Add a new file to the book folder named Index.cshtml and copy the following code into it:

@model IEnumerable<Author>
@{
                ViewBag.Title = “Authors and their books”;
}
<h1>@ViewBag.Title</h1>
@if(Model.Any()){
    <ul>
    @foreach(var author in Model){
        <li>@author.FirstName @author.LastName
            <ul>
            @foreach(var book in author.Books){
                <li>@book.Title</li>
            }
            </ul>
        </li>
    }
    </ul>
}
<div>@Html.ActionLink("New", "create")

Finally, add another file to the Views/Book folder named Create.cshtml and add the following code to it:

@model Book
@{
    ViewBag.Title = "New Book";
}

<h1>@ViewBag.Title</h1>

@using(Html.BeginForm()){
  <div class="form-group"
    @Html.LabelFor(model => model.AuthorId)
    @Html.DropDownListFor(model => model.AuthorId, (IEnumerable<SelectListItem>)ViewBag.Authors, string.Empty, new { @class="form-control"})
  </div>
  <div class="form-group">
    @Html.LabelFor(model => model.Title)
    @Html.TextBoxFor(model => model.Title, new { @class="form-control"})
  </div>
  <button type="submit" class="btn btn-default">Submit</button>
}

Execute the dotnet run command to build and run the application. You might need to press Ctrl + C to stop the application first. Once it is running again, navigate to http://localhost:5000/book/create where you should see a data entry screen like this:

The AuthorId dropdown should be populated with the the authors that you have so far entered into the application. Select one and enter a book title and hit the submit button. You should then be redirected to the Index view which will display a list of all authors and their books.



ASP.NET MVC Hosting - HostForLIFE.eu :: Prepare a Custom JSON Format in MVC or Remove JSON Key

clock January 9, 2020 11:15 by author Peter

This post explains how to remove a JSON key in JSON result in MVC or C#

We can create our own converter class:
    public class JsonKeysConverter : JsonConverter 
    { 
        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer) 
        { 
            Module o = (Module)value; 
            JObject newObject = new JObject(new JProperty(o.Name, o.Permission)); 
            newObject.WriteTo(writer); 
        } 
     
        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer) 
        { 
            throw new NotImplementedException("The type will skip the converter."); 
        } 
     
        public override bool CanRead 
        { 
            get { return false; } 
        } 
     
        public override bool CanConvert(Type objectType) 
        { 
            return true; 
        } 
    } 
     
    [JsonConverter(typeof(JsonKeysConverter))] 
    public class Module 
    { 
        public string Name { get; set; } 
        public string[] Permission { get; set; } 
    } 
     
    public class Role 
    { 
        public class Roles 
        { 
            public Dictionary<string, List<string>> Modules {get; set;} 
        } 
    } 
     
    public static string json() 
    { 
            var oRoles = new Roles(); 
            oRoles.modules = new Module[] { 
                new Module(){ 
                    Name="Page-Profile", 
                    Permission=new string[]{ "Edit","View","Delete"} 
                }, 
                new Module(){ 
                    Name="User", 
                    Permission=new string[]{ "Edit","View","Delete","Update"} 
                } 
            }; 
            var json = Newtonsoft.Json.JsonConvert.SerializeObject(oRoles); 
         
                     
            Dictionary<string, List<string>> modules = new Dictionary<string, List<string>>(); 
            modules.Add("Page-Profile", new List<string>() { "Edit", "View", "Delete"}); 
            modules.Add("User", new List<string>() { "Edit", "View", "Delete", "Update"}); 
             
            return JsonConvert.SerializeObject(modules);  


Output
{"Page-Profile":["Edit","View","Delete"],"User":["Edit","View","Delete","Update"]}  



ASP.NET MVC 6 Hosting United Kingdom - HostForLIFE.eu :: Compressing an ASP.NET MVC Response Manually

clock December 19, 2019 04:21 by author Peter

This post is regarding compression your http result while not using IIS Dynamic Compression. And this is code to compress ASP.NET MVC 6 Response Manually:

using System;
using System.IO.Compression;
using System.Web;
namespace WebCompressionSample
{
    public static class ResponseCompressor
    {
        public static void Compress(HttpContext context)
        {
           {
               return;
            }
            string acceptEncoding = context.Request.Headers["Accept-Encoding"];
            if (string.IsNullOrEmpty(acceptEncoding))
            {
                return;
            }
            if (acceptEncoding.IndexOf("gzip",
                StringComparison.OrdinalIgnoreCase) > -1)
            {
                       context.Response.Filter = new GZipStream(
                       context.Response.Filter, CompressionMode.Compress);
                       context.Response.AppendHeader("Content-Encoding", "gzip");

            }
            else if (acceptEncoding.IndexOf("deflate",
                StringComparison.OrdinalIgnoreCase) > -1)
            {
                    context.Response.Filter = new DeflateStream(
                    context.Response.Filter, CompressionMode.Compress);
                   context.Response.AppendHeader("Content-Encoding", "deflate");
            }
        }
    }
}

Well, this shows a way to do the compression itself. Looking on however you are doing ASP.NET MVC, you most likely can call it otherwise.In my case, I referred to as it manually from an ASP.NET Webforms PageMethod (more on why below), however if you're using ASP.NET MVC for instance, you most likely wish to wrap it in an ActionFilter and apply that to the action you wish to compress its output. Let me apprehend within the comments or on twitter if you've got a problem implementing it in a particular situation.

IIS 7+ has built in dynamic compression support (compressing output of server-side scripts like ASP.NET, PHP, etc.). It’s not by default as a result of compression dynamic content means that running the compression for each request (because it doesn’t know what the server-side script can generate for each request, the purpose of using server-side programming is generating dynamic content).

Static compression on the opposite side (caching static files like styles and scripts) is on by default as a result of once the static resource is compressed, the compressed version is cached and served for each future request of an equivalent file (unless the file changes of course). I’d say if your server side scripts expect to come large text-based content (say, large data, even when paging, etc. like large reports or whatever), always turn dynamic compression on, a minimum of for the pages that expect to come massive data sets of text.

In several cases though the majority of huge files will be scripts (and probably images) will be the larger components though, which are usually taken care of (for scripts for example) by IIS static compression or ASP.NET Bundling.



About HostForLIFE.eu

HostForLIFE.eu is European Windows Hosting Provider which focuses on Windows Platform only. We deliver on-demand hosting solutions including Shared hosting, Reseller Hosting, Cloud Hosting, Dedicated Servers, and IT as a Service for companies of all sizes.

We have offered the latest Windows 2016 Hosting, ASP.NET Core 2.2.1 Hosting, ASP.NET MVC 6 Hosting and SQL 2017 Hosting.


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