This control uses a mask to distinguish between proper and improper user input. For example: to force a user to fill out a date (e.g. a date of birth) in the masked text box a setting the property Mask to value of “90/90/0000” provides a text template for the user to type. Actual date value however should be validated by setting a regular expression validation.
Mask syntax:
The masked text box uses the standard Microsoft.NET MaskedTextProvider mask syntax (for full information see the .NET Framework SDK).
| Mask Character | Accepts | Required? |
| 0 | Digit (0-9) | Required |
| 9 | Digit (0-9) or space | Optional |
| # | Digit (0-9) or space | Required |
| L | Letter (a-z, A-Z) | Required |
| ? | Letter (a-z, A-Z) | Optional |
| & | Any character | Required |
| C | Any character | Optional |
| A | Alphanumeric (0-9, a-z, A-Z) | Required |
| a | Alphanumeric (0-9, a-z, A-Z) | Optional |
| . | Decimal separator | Required |
| , | Group (thousands) separator | Required |
| : | Time separator | Required |
| / | Date separator | Required |
| $ | Currency symbol | Required |
There is a few of other characters with special meaning:
| Mask Character | Meaning |
| < | All subsequent characters are converted to lower case |
| > | All subsequent characters are converted to upper case |
| | | Terminates a previous < or > sequence |
| \ | Escape: treat the next character in the mask as literal text rather than a mask symbol |