SignalR Database Update Notifications in ASP.NET MVC using SQL Dependency

• Download source code from Github

In this post, we will learn how to display real time updates from the SQL Server by using SignalR and SQL Dependency in ASP.NET MVC.

The following are the steps that we need to enable in the SQL Server first.

Step 1: Enable Service Broker on the Database

The following is the query that needs to enable the service broker:

ALTER DATABASE BlogDemos SET ENABLE_BROKER WITH ROLLBACK IMMEDIATE ;

Step 2: Add Connection String to the Web.Config File

<add name=&rdquo;DefaultConnection&rdquo; 
connectionString=&rdquo;Server=servername;

Database=databasename;User Id=userid;Password=password;&rdquo; 
providerName=&rdquo;System.Data.SqlClient&rdquo; />

Step 3: Enable SQL Dependency

In Global.asax, start the SQL Dependency in App_Start() event and Stop SQL dependency in the Application_End() event.

public class MvcApplication : System.Web.HttpApplication
    {
        string connString = ConfigurationManager.ConnectionStrings
        ["DefaultConnection"].ConnectionString;

        protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();
            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
            RouteConfig.RegisterRoutes(RouteTable.Routes);
            BundleConfig.RegisterBundles(BundleTable.Bundles);
            GlobalConfiguration.Configure(WebApiConfig.Register);
            //Start SqlDependency with application initialization
            SqlDependency.Start(connString);
        }

        protected void Application_End()
        {
            //Stop SQL dependency
            SqlDependency.Stop(connString);
        }
    }

Step 4: Install SignalR from the nuget

Run the following command in the Package Manager Console:

Install-Package Microsoft.AspNet.SignalR

Step 5: Create SignalR Hub Class

Create MessagesHub class in the Hubs folder:

public class MessagesHub : Hub
    {
        private static string conString = 
        ConfigurationManager.ConnectionStrings["DefaultConnection"].ToString();
        public void Hello()
        {
            Clients.All.hello();
        }

        [HubMethodName("sendMessages")]
        public static void SendMessages()
        {
            IHubContext context = GlobalHost.ConnectionManager.GetHubContext<MessagesHub>();
            context.Clients.All.updateMessages();
        }        
    }

Step 6: Get the Data from the Repository

Create MessagesRepository to get the messages from the database when data is updated.

public class MessagesRepository
    {
        readonly string _connString = 
        ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString;

        public IEnumerable<Messages> GetAllMessages()
        {
            var messages = new List<Messages>();
            using (var connection = new SqlConnection(_connString))
            {
                connection.Open();
                using (var command = new SqlCommand(@"SELECT [MessageID], 
                [Message], [EmptyMessage], [Date] FROM [dbo].[Messages]", connection))
                {
                    command.Notification = null;

                    var dependency = new SqlDependency(command);
                    dependency.OnChange += new OnChangeEventHandler(dependency_OnChange);

                    if (connection.State == ConnectionState.Closed)
                        connection.Open();

                    var reader = command.ExecuteReader();

                    while (reader.Read())
                    {
                        messages.Add(item: new Messages 
                        { MessageID = (int)reader["MessageID"], 
                        Message = (string)reader["Message"], 
                        EmptyMessage =  reader["EmptyMessage"] != DBNull.Value ? 
                        (string) reader["EmptyMessage"] : "", 
                        MessageDate = Convert.ToDateTime(reader["Date"]) });
                    }
                }              
            }
            return messages;            
        }

        private void dependency_OnChange(object sender, SqlNotificationEventArgs e)
        {
            if (e.Type == SqlNotificationType.Change)
            {
                MessagesHub.SendMessages();
            }
        }
    }

Step 7: Register SignalR at startup Class

Add the following code:

app.MapSignalR();

Step 8: View Page

Create div messagesTable that will append the table data from the database:

<div class="row">
    <div class="col-md-12">
       <div id="messagesTable"></div>
    </div>
</div>

Now add the SignalR related scripts in the page.

getAllMessages is a function that return the partialview data and bind it into the messagesTable div.

<script src="/Scripts/jquery.signalR-2.1.1.js"></script>
 <!--Reference the autogenerated SignalR hub script. -->
    <script src="/signalr/hubs"></script>

<script type="text/javascript">
    $(function () {
        // Declare a proxy to reference the hub.
        var notifications = $.connection.messagesHub;
       
        //debugger;
        // Create a function that the hub can call to broadcast messages.
        notifications.client.updateMessages = function () {
            getAllMessages()
           
        };
        // Start the connection.
        $.connection.hub.start().done(function () {
            alert("connection started")
            getAllMessages();
        }).fail(function (e) {
            alert(e);
        });
    });

    function getAllMessages()
    {
        var tbl = $('#messagesTable');
        $.ajax({
            url: '/home/GetMessages',
            contentType: 'application/html ; charset:utf-8',
            type: 'GET',
            dataType: 'html'
        }).success(function (result) {
            tbl.empty().append(result);
        }).error(function () {
            
        });
    }
</script>

Step 9: Create Partial View Page

Create a partial view _MessagesList.cshtml that returns all the messages.

@model IEnumerable<SignalRDbUpdates.Models.Messages>

<p>
    @Html.ActionLink("Create New", "Create")
</p>
<table class="table">
    <tr>
        <th>@Html.DisplayNameFor(model => model.MessageID)</th>
        <th>
            @Html.DisplayNameFor(model => model.Message)
        </th>
        <th>
            @Html.DisplayNameFor(model => model.EmptyMessage)
        </th>
        <th>
            @Html.DisplayNameFor(model => model.MessageDate)
        </th>
        
    </tr>

@foreach (var item in Model) {
    <tr>
        <td>
            @Html.DisplayFor(modelItem => item.MessageID)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.Message)
        </td>
        <th>
            @Html.DisplayFor(modelItem => item.EmptyMessage)
        </th>
        <td>
            @Html.DisplayFor(modelItem => item.MessageDate)
        </td>
        
    </tr>
}

</table>

Step 10: Set Up the Database

Create the database called blogdemos and run the following script:

USE [BlogDemos]
GO

/****** Object:  Table [dbo].[Messages]    Script Date: 10/16/2014 12:43:55 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[Messages](
	[MessageID] [int] IDENTITY(1,1) NOT NULL,
	[Message] [nvarchar](50) NULL,
	[EmptyMessage] [nvarchar](50) NULL,
	[Date] [datetime] NULL,
 CONSTRAINT [PK_Messages] PRIMARY KEY CLUSTERED 
(
	[MessageID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, _
IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

GO

ALTER TABLE [dbo].[Messages] ADD  CONSTRAINT [DF_Messages_Date]  DEFAULT (getdate()) FOR [Date]
GO

Step 11: Run the Project

When eve data is inserted into the table, the dependency_OnChange method will fire.

You can download the source from Github.

The post SignalR Database update notifications in ASP.NET MVC using SQL Dependency appeared first on Venkat Baggu Blog.