Webapi call from not signalr client in Web Application with Signalr and Webapi

Question

User-2715168 posted

I have created a MVC5 Web Application with Webapi included.  It also has signalr.  My problem is when I call an api controller from a non signalr client the code executes to get the hub context but does not fire on the clients.  If I call the same webapi endpoint from a signalr client then signalr calls the clients properly.  I have a windows service that updates database but does not need to be a signalr client.  So it calls a webapi endpoint.  I want this to notify signalr clients in the same webapplication.  Can this be done or is there a better way?

Answer 1

User61956409 posted

Hi glfcstman,

I want this to notify signalr clients in the same webapplication.  Can this be done or is there a better way?

If you'd like to push updates/data to web application clients by calling hub method from your Web API action, the approach you mentioned should be able to help achieve the requirement.

My problem is when I call an api controller from a non signalr client the code executes to get the hub context but does not fire on the clients.  If I call the same webapi endpoint from a signalr client then signalr calls the clients properly.

To reproduce the scenario you mentioned, I create a simple sample like below, which work well on my side, you can refer to it.

Hub class

public class ChatHub : Hub
{
    public void Send(string name, string message)
    {
        // Call the addNewMessageToPage method to update clients.
        Clients.All.addNewMessageToPage(name, message);
    }
}

MVC client

<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 src="~/Scripts/jquery.signalR-2.4.1.min.js"></script>
    <script src="~/signalr/hubs"></script>

    <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>
}

Web API

[Route("api/GetUpdates")]
public IEnumerable<string> Get()
{
    var hubContext = GlobalHost.ConnectionManager.GetHubContext<ChatHub>();
    hubContext.Clients.All.addNewMessageToPage("API", "test data from API");

    return new string[] { "value1", "value2" };
}

Console client (in your scenario, it would be a windows service application)

HttpClient httpClient = new HttpClient();
HttpResponseMessage res = httpClient.GetAsync("http://localhost:51613/api/getupdates").Result;

if (res.StatusCode== HttpStatusCode.OK)
{
    Console.WriteLine("Updates have been pushed to clients.");
}
else
{
    Console.WriteLine("Pushing updates failed.");
}

Test Result

With Regards,

Fei Han