WPF

// Attempt to create an instance of the proxy
bool serviceRunning = true;
try
{
    Proxy = new MyAppServiceRef.MyAppServiceClient();
}
catch (Exception e)
{
    serviceRunning = false;
}
// Now check to see if the service is running
try
{
    serviceRunning = !Proxy.ServiceRunning();
}
catch (Exception e)
{
    serviceRunning = false;
}

// If the service is not running, then exit the app
if (!serviceRunning)
{
    string message = "The service appears to not be running. Please check the service. " + ApplicationTitle + " will now exit.";
    MessageBox.Show(message, "Service Error", MessageBoxButton.OK, MessageBoxImage.Stop);
    Application.Current.Shutdown();
}

namespace WpfApplication22
{
public partial class App : Application
{


[DllImport("user32.dll", CharSet = CharSet.Auto)]
static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam);

private const int APPCOMMAND_XXX = 0x80000;

private void MetodoMute(object sender, EventArgs e)
// Mute
        {
            SendMessageW(this.Handle, WM_APPCOMMAND, this.Handle,
                (IntPtr)APPCOMMAND_xxx);

        }
}
}

private void button4_Click(object sender, RoutedEventArgs e)
{
    App x = new App();
    x.MetodoMute(new WindowInteropHelper(this).Handle);

}