Ok, no code to help, but what you need to basically do is this:
string myString = string.Empty;
MyService.MyMethodAsync();
MyMethodCompleted += new Eventhandler<mymethodcompletedeventargs>(MyEventHandler);
void MyEventHandler(object sender, MyMethodCompletedEventArgs e)
{
myString = e.Result;
}
</mymethodcompletedeventargs>