Lets take the Credit Card Input on the Example-Page:

It's prefilled with

1234 1234 1234 1234

When my Number is 1234 1299 1234 1234 i don't want to type it all again, but i set my focus behind the second 2 and start Typing 99

focus: 1234 12|34 1234 1234

value after typing: 1234 1299 3412 3412

expected value: 1234 1299 1234 1234

The MaskedTextbox seems to insert typed characters and push every other input down in the Mask. But since i am having a Mask when i move to a position, i want to overwrite that single place - leaving the rest of the input intact.