silverlight 文本框只能输入数字

void mobile_KeyUp(object sender, KeyEventArgs e)

        {

            Regex rg = new Regex("^[0-9]{1,11}$");

            Regex rg1 = new Regex("\b");

            if (!rg.IsMatch(mobile.Text) && !rg1.IsMatch(e.Key.ToString()))

            {

                if (mobile.Text.Length > )

                {

                    mobile.Text = mobile.Text.Substring(, mobile.Text.Length - );

                    mobile.SelectionStart = mobile.Text.Length;

                }

                else

                {

                    mobile.Text = "";

                }

            }

        }