public void HelloWorld(Message msg) { // Get context ICallback callback = OperationContext.Current.GetCallbackChannel <ICallback>(); if (msg.IsEmpty || ((IChannel)callback).State != CommunicationState.Opened) { return; } string txt = Encoding.UTF8.GetString(msg.GetBody <byte[]>()); // Callback client try { callback.BroadcastToNetClient(CreateSoapMessage($"Hello {txt}")); } catch { callback.BroadcastToBrowserClient(CreateByteArrayMessage($"Hello {txt}")); } }