Gets a value that specifies whether new user input overwrites existing input.
Assembly: System.Windows.Forms (in System.Windows.Forms.dll)
takes into account both the value of the InsertKeyMode property and the state of the user's keyboard. If InsertKeyMode is set to either Insert or Overwrite, will return false or true, respectively. If InsertKeyMode is set to Default, it will return the state of the INSERT key.
When is false, MaskedTextBox will reject as invalid any character entry that would result in a violation anywhere in the mask. In explanation, if inserting a character would cause a character to be shifted over into a mask position where it would not be valid, the character insertion will be rejected.