Imports System
Imports Xceed.Editors 

Namespace Xceed.Editors.Samples
  Public Class CustomTextBoxArea
    Inherits TextBoxArea 

Public Sub New( ByVal textBox As WinTextBox )
  MyBase.New( textBox )
End Sub 

Protected Overrides ReadOnly Property MaskChars() As Char()
  Get
    Dim chars( MyBase.MaskChars.Length + 1 ) As Char
    MyBase.MaskChars.CopyTo( chars, 0 )
    chars( MyBase.MaskChars.Length ) = "$"c 

    Return chars
  End Get
End Property 

Protected Overrides Function IsCharValid( ByVal maskChar As Char, _
                                          ByVal charToValidate As Char ) As Boolean

Dim valid As Boolean = MyBase.IsCharValid( maskChar, charToValidate ) 

If Not valid Then
  If ( maskChar = "$"c And charToValidate = "+"c Or _
       charToValidate = "-"c Or charToValidate = "*"c Or _
       charToValidate = "/"c ) Then 

    valid = True
  End If
End If

Return valid

End Function

End Class
End Namespace