wpf中文本框只能输入整数

private void txtBarCodeNum_KeyUp(object sender, KeyEventArgs e)
        {
            TxtInt(sender as TextBox);
        }

        private void txtBarCodeNum_TextChanged(object sender, TextChangedEventArgs e)
        {
            TxtInt(sender as TextBox);
        }

        private void TxtInt(TextBox txt)
        {
            if (txt==null || string.IsNullOrEmpty(txt.Text))
            {
                txt.Tag = "";
                return;
            }
            try
            {
                txt.Text = txt.Text.Trim();
                txt.Tag = Convert.ToInt32(txt.Text); ;
            }
            catch
            {
                if (txt.Tag==null)
                {
                    txt.Text = "";
                }
                else
                {
                    txt.Text = txt.Tag.ToString();
                }
            }
            txt.SelectionStart = txt.Text.Length;
        }