public override Task OnDisconnectedAsync(Exception exception)
 {
     HubConnectionStore.RemoveUserConnection(Context.UserIdentifier, Context.ConnectionId);
     return(base.OnDisconnectedAsync(exception));
 }
 public override Task OnConnectedAsync()
 {
     HubConnectionStore.AddUserConnection(Context.UserIdentifier, Context.ConnectionId);
     return(base.OnConnectedAsync());
 }