protected override void OnDetaching()
{
Masking.SetMask(attachedTextBox, null);
attachedTextBox = null;
base.OnDetaching();
}
private void AttachTextBox(TextBox textBox)
{
attachedTextBox = textBox;
Masking.SetMask(attachedTextBox, @"^[a-zA-Z][a-zA-Z0-9\._-]*$");
}