How does Vibrator fire in my Windows Phone 8.1 app?

As for example:

 if(==0)
 {
 VIBRAR APARELHO;
 }

You can use the command VibrateController as in the example below:

import Microsoft.Devices

VibrateController testVibrateController = VibrateController.Default;

if(Vibrar = true)
{
    testVibrateController.Start(TimeSpan.FromSeconds(3));
    testVibrateController.Stop();
}