Hi,
The System.Windows.Forms.MaskedTextBox doesn't support the function you want so far. I suggest that you create a new class derived from the TextBox class, which only allows numbers in it.
The base class can be System.Windows.Forms.TextBox or the System.Windows.Controls.TextBox class. For the former case, you need to host the custom control usingthe WindowsFormsHostin your WPF application; for the latter case, you can use it in the WPF application directly.
Hope this helps.
If you have any question, please feel free to let me know.
Linda