Signalr has no connetions - asp.net-web-api

Question

I'm trying to use signalr in ApiController that handles upload from a page.
Essentially I am invoking my Hub from my uploadController and then I want to talk to my client.
shortened down the upload controller looks like this:
public class UploadController : ApiController
{
public Task<HttpResponseMessage> PostFile()
{
var hubMan = new HubManager();
hubMan.showUpload("test");
}
}
I then have my HubManager that should take care of sending to my client:
public class HubManager : Hub
{
public HubManager()
{
}
public void showUpload(string src)
{
Caller.showUpload(src);
}
}
I also tried this in my showUpload:
public void showUpload(string str)
{
var context = GlobalHost.ConnectionManager.GetHubContext<HubManager>();
context.Clients[this.Context.ConnectionId].showUpload(str);
}
My client side code looks like this:
$(document).ready(function () {
var progress = $.connection('/signalr/hubs/hubManager');
progress.showUpload = function (src) {
alert(src);
};
// Start the connection
$.connection.hub.start();
});
Now the problem is that in my Hub class everything is Null.
My Caller,Clients and Context is null. So it seems something is not initialising properly.
Any suggestions?

Answer 1

You cannot create an instance of a SignalR hub yourself. Hubs need to be initialized by SignalR so the properties like Clients etc. are available.
If you want to broadcast to clients from outside the hub (e.g. your controller), you need to use the context object of the hub as described in the wiki:
public ActionResult ControllerAction()
{
var context = GlobalHost.ConnectionManager.GetHubContext<HubManager>();
context.Clients[ /* connectionId or group name */ ].showUpload();
// ...
}
Please note that you can't access context.ConnectionId or context.Caller there, because you are calling your ApiController and not SignalR, so the framework knows nothing about the ConnectionId in this case. You need to pass it to the controller in some other way, e.g. cookies or as a parameter of the controller action.