How to obtain connection ID of signalR client on the server side?

Question

I need to get the connection ID of a client. I know you can get it from the client side using $.connection.hub.id. What I need is to get in while in a web servi

Answer 1

Taylor's answer works, however, it doesn't take into consideration a situation where a user has multiple web browser tabs opened and therefore has multiple different connection IDs.

To fix that, I created a Concurrent Dictionary where the dictionary key is a user name and the value for each key is a List of current connections for that given user.

public static ConcurrentDictionary> ConnectedUsers = new ConcurrentDictionary>();

On Connected - Adding a connection to the global cache dictionary:

public override Task OnConnected()
{
    Trace.TraceInformation("MapHub started. ID: {0}", Context.ConnectionId);
    
    var userName = "testUserName1"; // or get it from Context.User.Identity.Name;

    // Try to get a List of existing user connections from the cache
    List existingUserConnectionIds;
    ConnectedUsers.TryGetValue(userName, out existingUserConnectionIds);

    // happens on the very first connection from the user
    if(existingUserConnectionIds == null)
    {
        existingUserConnectionIds = new List();
    }

    // First add to a List of existing user connections (i.e. multiple web browser tabs)
    existingUserConnectionIds.Add(Context.ConnectionId);

    
    // Add to the global dictionary of connected users
    ConnectedUsers.TryAdd(userName, existingUserConnectionIds);

    return base.OnConnected();
}

On disconnecting (closing the tab) - Removing a connection from the global cache dictionary:

public override Task OnDisconnected(bool stopCalled)
{
    var userName = Context.User.Identity.Name;

    List existingUserConnectionIds;
    ConnectedUsers.TryGetValue(userName, out existingUserConnectionIds);

    // remove the connection id from the List 
    existingUserConnectionIds.Remove(Context.ConnectionId);

    // If there are no connection ids in the List, delete the user from the global cache (ConnectedUsers).
    if(existingUserConnectionIds.Count == 0)
    {
        // if there are no connections for the user,
        // just delete the userName key from the ConnectedUsers concurent dictionary
        List garbage; // to be collected by the Garbage Collector
        ConnectedUsers.TryRemove(userName, out garbage);
    }

    return base.OnDisconnected(stopCalled);
}