Getting Started with SignalR and MVC 5

This post introduces you to real-time web application development with ASP.NET SignalR and ASP.NET MVC 5. 

In this post you will learn the following SignalR development tasks:

• Adding the SignalR library to an MVC 5 application.
• Creating hub and OWIN startup classes to push content to clients.
• Using the SignalR jQuery library in a web page to send messages and display updates from the hub.

Prerequisites: 

• Visual Studio 2013. If you do not have Visual Studio, see ASP.NET Downloads to get the free Visual Studio 2013 Express Development Tool.

This section shows how to create an ASP.NET MVC 5 application, add the SignalR library, and create the chat application.

1. In Visual Studio, create a C# ASP.NET application that targets .NET Framework 4.5, name it SignalRChat, and click OK.
   
2. In the New ASP.NET Project dialog, and select MVC, and click Change Authentication.
   
3. Select No Authentication in the Change Authentication dialog, and click OK.
   
   Note: If you select a different authentication provider for your application, a Startup.cs class will be created for you; you will not need to create your own Startup.cs class in step 10 below.
4. 1. Click OK in the New ASP.NET Project dialog.
   2. Open the Tools | Library Package Manager | Package Manager Console and run the following command. This step adds to the project a set of script files and assembly references that enable SignalR functionality.
      install-package Microsoft.AspNet.SignalR
   3. In Solution Explorer, expand the Scripts folder. Note that script libraries for SignalR have been added to the project.
      
   4. In Solution Explorer, right-click the project, select Add | New Folder, and add a new folder named Hubs.
   5. Right-click the Hubs folder, click Add | New Item, select the Visual C# | Web | SignalR node in the Installedpane, select SignalR Hub Class (v2) from the center pane, and create a new hub named ChatHub.cs. You will use this class as a SignalR server hub that sends messages to all clients.
      
   6. Replace the code in the ChatHub class with the following code.

      using System;
      using System.Web;
      using Microsoft.AspNet.SignalR;
      namespace SignalRChat
      {
          public class ChatHub : Hub
          {
              public void Send(string name, string message)
              {
                  // Call the addNewMessageToPage method to update clients.
                  Clients.All.addNewMessageToPage(name, message);
              }
          }
      }

   7. Create a new class called Startup.cs. Change the contents of the file to the following.

      using Owin;
      using Microsoft.Owin;
      [assembly: OwinStartup(typeof(SignalRChat.Startup))]
      namespace SignalRChat
      {
          public class Startup
          {
              public void Configuration(IAppBuilder app)
              {
                  // Any connection or hub wire up and configuration should go here
                  app.MapSignalR();
              }
          }
      }

   8. Edit the HomeController class found in Controllers/HomeController.cs and add the following method to the class. This method returns the Chat view that you will create in a later step.

      public ActionResult Chat()
      {
          return View();
      }

   9. Right-click the Views/Home folder, and select Add... | View.
   10. In the Add View dialog, name the new view Chat.
       
   11. Replace the contents of Chat.cshtml with the following code.

       Important: When you add SignalR and other script libraries to your Visual Studio project, the Package Manager might install a version of the SignalR script file that is more recent than the version shown in this topic. Make sure that the script reference in your code matches the version of the script library installed in your project.

       @{
           ViewBag.Title = "Chat";
       }
       <h2>Chat</h2>
       <div class="container">
           <input type="text" id="message" />
           <input type="button" id="sendmessage" value="Send" />
           <input type="hidden" id="displayname" />
           <ul id="discussion">
           </ul>
       </div>
       @section scripts {
           <!--Script references. -->
           <!--The jQuery library is required and is referenced by default in _Layout.cshtml. -->
           <!--Reference the SignalR library. -->
           <script src="~/Scripts/jquery.signalR-2.1.0.min.js"></script>
           <!--Reference the autogenerated SignalR hub script. -->
           <script src="~/signalr/hubs"></script>
           <!--SignalR script to update the chat page and send messages.--> 
           <script>
               $(function () {
                   // Reference the auto-generated proxy for the hub.  
                   var chat = $.connection.chatHub;
                   // Create a function that the hub can call back to display messages.
                   chat.client.addNewMessageToPage = function (name, message) {
                       // Add the message to the page. 
                       $('#discussion').append('<li><strong>' + htmlEncode(name) 
                           + '</strong>: ' + htmlEncode(message) + '</li>');
                   };
                   // Get the user name and store it to prepend to messages.
                   $('#displayname').val(prompt('Enter your name:', ''));
                   // Set initial focus to message input box.  
                   $('#message').focus();
                   // Start the connection.
                   $.connection.hub.start().done(function () {
                       $('#sendmessage').click(function () {
                           // Call the Send method on the hub. 
                           chat.server.send($('#displayname').val(), $('#message').val());
                           // Clear text box and reset focus for next comment. 
                           $('#message').val('').focus();
                       });
                   });
               });
               // This optional function html-encodes messages for display in the page.
               function htmlEncode(value) {
                   var encodedValue = $('<div />').text(value).html();
                   return encodedValue;
               }
           </script>
       }

   12. Save All for the project.

   Run the Sample

1. Press F5 to run the project in debug mode.
2. In the browser address line, append /home/chat to the URL of the default page for the project. The Chat page loads in a browser instance and prompts for a user name.
   
3. Enter a user name.
4. Copy the URL from the address line of the browser and use it to open two more browser instances. In each browser instance, enter a unique user name.
5. In each browser instance, add a comment and click Send. The comments should display in all browser instances.

   Note: This simple chat application does not maintain the discussion context on the server. The hub broadcasts comments to all current users. Users who join the chat later will see messages added from the time they join.

6. The following screen shot shows the chat application running in a browser.
   
7. In Solution Explorer, inspect the Script Documents node for the running application. This node is visible in debug mode if you are using Internet Explorer as your browser. There is a script file named hubs that the SignalR library dynamically generates at runtime. This file manages the communication between jQuery script and server-side code. If you use a browser other than Internet Explorer, you can also access the dynamic hubsfile by browsing to it directly, for example http://mywebsite/signalr/hubs.

The SignalR chat application demonstrates two basic SignalR development tasks: creating a hub as the main coordination object on the server, and using the SignalR jQuery library to send and receive messages.

SignalR Hubs

In the code sample the ChatHub class derives from the Microsoft.AspNet.SignalR.Hub class. Deriving from theHub class is a useful way to build a SignalR application. You can create public methods on your hub class and then access those methods by calling them from scripts in a web page.

In the chat code, clients call the ChatHub.Send method to send a new message. The hub in turn sends the message to all clients by calling Clients.All.addNewMessageToPage.

The Send method demonstrates several hub concepts :

• Declare public methods on a hub so that clients can call them.
• Use the Microsoft.AspNet.SignalR.Hub.Clients property to access all clients connected to this hub.
• Call a function on the client (such as the addNewMessageToPage function) to update clients.

  public class ChatHub : Hub
  {
      public void Send(string name, string message)
      {
          Clients.All.addNewMessageToPage(name, message);
      }
  }

SignalR and jQuery

The Chat.cshtml view file in the code sample shows how to use the SignalR jQuery library to communicate with a SignalR hub. The essential tasks in the code are creating a reference to the auto-generated proxy for the hub, declaring a function that the server can call to push content to clients, and starting a connection to send messages to the hub.

The following code declares a reference to a hub proxy.

var chat = $.connection.chatHub; 

Note: In JavaScript the reference to the server class and its members is in camel case. The code sample references the C# ChatHub class in JavaScript as chatHub. If you want to reference the ChatHub class in jQuery with conventional Pascal casing as you would in C#, edit the ChatHub.cs class file. Add a using statement to reference the Microsoft.AspNet.SignalR.Hubs namespace. Then add the HubName attribute to the ChatHub class, for example [HubName("ChatHub")]. Finally, update your jQuery reference to the ChatHub class.

The following code shows how to create a callback function in the script. The hub class on the server calls this function to push content updates to each client. The optional call to the htmlEncode function shows a way to HTML encode the message content before displaying it in the page, as a way to prevent script injection.

chat.client.addNewMessageToPage = function (name, message) {
    // Add the message to the page. 
    $('#discussion').append('<li><strong>' + htmlEncode(name) 
        + '</strong>: ' + htmlEncode(message) + '</li>');
};

The following code shows how to open a connection with the hub. The code starts the connection and then passes it a function to handle the click event on the Send button in the Chat page.

Note: This approach ensures that the connection is established before the event handler executes.

$.connection.hub.start().done(function () {
    $('#sendmessage').click(function () {
        // Call the Send method on the hub. 
        chat.server.send($('#displayname').val(), $('#message').val());
        // Clear text box and reset focus for next comment. 
        $('#message').val('').focus();
    });
});