MessageBoxResult result = MessageBox.Show("Would you like to greet the world with a "Hello, world"?", "My App", MessageBoxButton.YesNoCancel);
switch(result)
{
case MessageBoxResult.Yes:
MessageBox.Show("Hello to you too!", "My App");
break;
case MessageBoxResult.No:
MessageBox.Show("Oh well, too bad!", "My App");
break;
case MessageBoxResult.Cancel:
MessageBox.Show("Nevermind then...", "My App");
break;
}