PlaceholderCharacter
Single character used as a placeholder for the input mask. This can be used as sample input until the user fills the input mask. For the telephone number input mask mentioned in the above example, you could include a sample digit as the placeholder such as 9. At runtime it would appear as (999) 999- 9999 until the user replaced these digits with their own.
Note: This field accepts a single character only. If the Placeholder is set to '_' in the example above, at runtime it would appear as ( ) - . Likewise, if the placeholder is set to '?' at runtime it would appear as (???) ???-????.