How to dismiss a MessageDialog from code in Windows Phone 8.1

How can I dismiss a Message dialog programmatically in Windows Phone 8.1. I created the dialog using showAsync(). If this is not possible which is the best method to create a custom message dialog with the following properties:

1. It can show test and hold buttons for user interaction.
2. It can be dismissed programmatically
3. Should block the view as a Normal MessageDialog do