c#中textbox只能输入数字和小数点

         private void txt1xv_KeyPress(object sender, KeyPressEventArgs e)
        {
            int keyValue = (int)e.KeyChar;
            if ((keyValue >= 48 && keyValue <= 57) || keyValue == 8 || keyValue == 46)
            {
                if (sender != null && sender is TextBox && keyValue == 46)
                {
                    if (((TextBox)sender).Text.IndexOf(".") >= 0)
                        e.Handled = true;
                    else
                        e.Handled = false;
                }
                else
                    e.Handled = false;
            }
            else
                e.Handled = true;
        }