public async Task JoinRoom(string groupId) { var user = ConnectedUsers.Users.FirstOrDefault(x => x.UID == Context.UserIdentifier); if (user != default) //user exist { if (ActiveGroups.GetGroup(groupId) != default) //Group exist { AddToGroup(groupId, user); await Clients.Caller.GoToRoom(groupId); } else { await Clients.Caller.ReceiveMessage("InvalidGroup"); } } }