CODEWITHSUNDEEP
c#javascriptsignalr
user516883
user516883

Reputation: 9408

How to join a group using SignalR

I am new to using SignalR (started today), Pretty simple to send a message to ALL clients connected, but now I want to just send to a group. I cannot find simple documentation on how to join on the client side. If anyone can help, how can I SIMPLY join a group on the javascript side. Thanks for any help.

public class EventHub : Hub
{
    public void SendNewMedia(MediaInfoViewModel model,Guid eventId)
    {
        Clients.Group(eventId.ToString()).setupmedia(model);
    }
}
//Controller that is sending client new data
var eventHub = GlobalHost.ConnectionManager.GetHubContext<EventHub>();
              var result = eventHub.Clients.Group(eventId.ToString()).setupmedia(eventViewer);

//Finally the javascript. Not sure how to setup just for a group
$(function () {
    var event = $.connection.eventHub;
    event.client.setupmedia = function (newMedia) {

        $('#photolist').prepend('<li><img src="' + newMedia.MediaUrl + '" class="img-polaroid span2"/></li>');
    };
    $.connection.hub.start(function() {
        event.server.create(eventID);//I know this is wrong but not sure how to connect
    }).done(function () {
        alert('conntected. Ready to retrieve data!');
    });
});

Upvotes: 26

Views: 42806

Answers (3)

jaba_y
jaba_y

Reputation: 582

-------------------------In Javascript (ReactJs)---------------------------------

const connection = new signalR.HubConnectionBuilder()
  .withUrl("connectionUrl")
  .build();
connection.start().then(res => {
    connection.invoke("JoinGroup", "groupName")  //JoinGroup is C# method name
        .catch(err => {
            console.log(err);
        });
}).catch(err => {
            console.log(err);
        });;

----------------In C# (.Net Core)-----------------

public class NotificationHub : Hub
    {
        public Task JoinGroup(string groupName)
        {
                return Groups.AddToGroupAsync(Context.ConnectionId, groupName);
        }
    }

Upvotes: 15

JCisar
JCisar

Reputation: 2674

Just in case you come across this question now (like I did), here is an example for how to implement an azure function to support groups.

https://learn.microsoft.com/en-us/azure/azure-functions/functions-bindings-signalr-service#2x-c-group-management-output-examples

Upvotes: 2

Nikola Dimitroff
Nikola Dimitroff

Reputation: 6237

You can't. If you could join a group from javascript then anyone may use your code to join any group which breaks security. If you really need to do that - create a method on the server side that takes a group name as parameter and adds the client to the group.

public void JoinGroup(string groupName)
{
    this.Groups.Add(this.Context.ConnectionId, groupName);
}

Afterwards, call it from JS like that

eventHub.server.joinGroup("my-awsm-group");

Upvotes: 44

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