_Telephone = new RadMaskedInput
            { 
                Mask = "[(][0-9]{3}[)] [0-9]{3}-[0-9]{4}",
                MaskType = MaskType.Regex,
                WatermarkText = "Phone # (999) 999-9999",
                RejectedSymbolErrorText = "Only Numbers Allowed!",
                InvalidInputErrorText = "Invalid Input",
                WatermarkTextColor = Color.Black,
                ErrorColor = Color.Red,
                DisplayedTextColor = Color.Black,
            };

            _Telephone.InputValue = "2223334444";
            Grid.Children.Add(_Telephone, 0, 0);