calling SignalR hub from WebAPI controller issues

2019-01-14 08:56发布

站内文章 / C#
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问题:

I cannot figure out how I can call into a SignalR hub from a WebAPI ApiController. I have put together a sample you can download here that simplifies the problem and demonstrates the issue.

  1. I created a new project from the ASP.NET MVC WebAPI template.
  2. I added a new SignalR Hub to the project called ChatHub.
  3. Added a HTML page that on load, connects to ChatHub, joins to a group and sends a message to that group. This works great.
  4. HTML page also has a button that when clicked will fire an ajax call to the ValuesController's post method. In the ValuesController's post method, I want to broadcast a message to all the connected clients of the group. I cannot get this to work.

I have a simple SignalR hub with just 2 methods.

[HubName("chat")]
public class ChatHub : Hub
{
    public void Join(string room)
    {
        // NOTE: this is not persisted - ....
        Groups.Add(Context.ConnectionId, room);
    }

    public void Send(string room, string message)
    {
        var msg = String.Format(
            "{0}: {1}", Context.ConnectionId, message);
        Clients.Group(room).newMessage(msg);
    }
}

I created a very simple HTML page that connects to the Chat hub when the DOM is ready as shown here.

<html>
<head>
    <title>Simple Chat</title>
    <script src="Scripts/jquery-1.8.2.js" type="text/javascript"></script>
    <script src="Scripts/jquery.signalR-1.0.0.js"></script>
    <script src="signalr/hubs"></script>
    <script type="text/javascript">
        var chat;

        //$(function () {
        //    connectToHubs();
        //});
        $(connectToHubs);
        function connectToHubs() {
            $.connection.hub.logging = true;

            chat = $.connection.chat;
            chat.client.newMessage = onNewMessage;

            $.connection.hub.start({ transport: 'longPolling' }).done(function () {
                chat.server.join("TestGroup").done(function () {
                    chat.server.send("TestGroup", "message from html");
                });
            });

            $('#controller').click(postProficiencyUserAction);



        }
        var postProficiencyUserAction = function () {
            //var token = $('[name=__RequestVerificationToken]').val();
            var headers = {};
            //headers["__RequestVerificationToken"] = token;
            //var userAction = { createdOn: "2013-05-21T00:00:00", userId: "12345678-1234-1234-1234-000000000001", actionId: "12345678-1234-1234-1234-000000000003" };
            $.ajax({
                type: 'POST',
                url: 'http://localhost:58755/api/values',
                cache: false,
                headers: headers,
                contentType: 'application/json; charset=utf-8',
                data: 'test',
                dataType: "json",
                success: function () {

                },
                error: function () {

                }
            });
        };
        function onNewMessage(message) {
            // ... todo: validation !!!! :)
            $('#messages').append('<li>' + message + '</li>');
        };

    </script>
</head>
<body>
    <div>
        <h2>Chat</h2>
        <input type="button" id="controller" value="Controller Method" />
        <div>
            <h2>Message(s) Received</h2>
            <ul id="messages"></ul>
        </div>
    </div>
</body>
</html>

Nothing fancy. Whenever the connected hub receives a new message, a new item is added to the unordered list. There is a button that makes an Ajax call into the ValuesController post method.

public class ValuesController : ApiController
{
    // POST api/values
    public void Post([FromBody]string value)
    {
        var hubContext = GlobalHost.ConnectionManager.GetHubContext<ChatHub>();
        hubContext.Clients.Group("TestGroup").send("TestGroup", "Called from Controller");
    }

The Hub call does not work. An error is not thrown, but, the message is never received. Putting a breakpoint in the "Send" method of the Hub does not work either. I feel like I am doing it right. Anyone help? Again, source code can be found here

回答1:

You are calling different methods on the client:

API controller

hubContext.Clients.Group("TestGroup").send("TestGroup", "Called from Controller");

Hub

Clients.Group(room).newMessage(msg);

The method you want to call is newMessage not send

chat.client.newMessage = onNewMessage;


标签： c# signalr
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