文本框只能輸入數字的方法

private void BBBTBox_KeyPress(object sender, KeyPressEventArgs e)
        {

            if (BBBTBox.SelectionStart == 0)
            {
                if (e.KeyChar.CompareTo('0') == 0 || e.KeyChar.CompareTo('0') < 0 || e.KeyChar.CompareTo('9') > 0)
                {
                    e.Handled = true;
                }
            }
            else
            {
                if (e.KeyChar.CompareTo('0') < 0 || e.KeyChar.CompareTo('9') > 0)
                {
                    if (e.KeyChar != '/b')
                    {
                        e.Handled = true;
                    }
                }
            }
        }