The MaskedTextBox control provides a validation procedure for inputs on the form like date, phone numbers, etc entered by the user. MaskedTextBox provides a mask, which validates proper user input, and invalidates improper inputs. In MaskedTextBox control, you can mask the input using Mask Property, which will be used at runtime to enter some specific type of input in the box.

The MaskInfo class provides the RegexpMaskType property, which is used to set the mask expression style. The RegexpMaskType enumeration is used to determine RegexpEditMask pattern processing and validation. It can take any one of the following two values:

• C1RegexpEditMask, which uses custom parser. It don't support complicated regular expressions. It provides edit mask for user input. It can be validated during entering text, and
• RegexpMask, which is based on MS Regex with some restrictions for available keywords. It will not provide any edit mask. It can be validated on exit from edit mode only.