RadMaskedTextInput. Value is 12345. Select All. Then press "A" (or random key) while down, press space key and then release it (this happens when you type fast). Expected: Value is "A ". Actual Value is " " (A is removed). Workaround: public class CustomInput : RadMaskedTextInput { protected override void OnKeyDown(KeyEventArgs e) { if (this.Value != null && this.SelectionLength == this.Value.Length && this.SelectionLength > 0) { this.ClearCommand.Execute(null); } base.OnKeyDown(e); } }