C# async callback to return value

I am having async web service call which should return Bool value true or false. Below is code on how i am calling this web service: private string msgStatus; public bool GetNotifyStatus (string Data) { [login to view URL] (Data); [login to view URL] (); return msgStatus; } Then i have completed Event handler that actually gets value private void ClientGetNotifyStatusCompleted (object sender, GetNotifyStatusCompletedEventArgs er) { msgStatus = [login to view URL]; [login to view URL] (); } the problem is that my UI just hangs after execution of this code, but when i am using service interface which is returning one [login to view URL] everythings works. this interface can return multiple results. [login to view URL], er ResultData2