关于textbox或combobox限制输入内容

private void comboBox3_KeyPress( object sender, KeyPressEventArgs e )
{
//e.KeyChar < 48 || e.KeyChar > 57表示0-9的数字
//e.KeyChar != 46 表示小数点
//e.KeyChar != 8 表示退格键
//e.KeyChar != 3  e.KeyChar != 22 表示复制、粘贴
if ((e.KeyChar < 48 || e.KeyChar > 57) && (e.KeyChar != 46) && e.KeyChar != 8)
{
MessageBox.Show( "请输入数字" );
e.Handled = true;
}else if (char.IsPunctuation(e.KeyChar))
{
if (comboBox3.Text.LastIndexOf( '.' ) != -1)
{
e.Handled = true;
MessageBox.Show( "只能输入一个小数点" );
}
}
}
private void comboBox3_TextChanged( object sender, EventArgs e )
{
//若小数点在第一位,则在前面加0
if (comboBox3.Text.Substring( 0 ) == ".")
{
this.comboBox3.Text = "0.";
comboBox3.SelectionStart = 2;
}
}
private void textBox5_KeyPress( object sender, KeyPressEventArgs e )
        {
            if ((e.KeyChar < 48 || e.KeyChar > 57) && e.KeyChar != 8)
            {
                e.Handled = true;
                MessageBox.Show( "只允许输入整数" );
            }
        }
正则表达式验证decimal(n,m)数据类型:
1、通过写类，textbox或者combobox调用验证
 /// <summary>
        /// 匹配decimal(n,m)
        /// </summary>
        /// <param name="tb"></param>
        /// <returns></returns>
        public static bool nmDecimal( TextBox tb )
        {
            bool res = Regex.IsMatch( tb.Text, @"^\d{1,n-m}(?:\.\d{1,m})?$" );
            return res;
        }
调用方法:
private void textBox27_LostFocus( object sender, EventArgs e )
        {
//DateDay类名称
             if (!DateDay.nmDecimal( textBox27 ))
            {
                this.textBox27.Text = "";
                MessageBox.Show( "只允许输入整数部分最多(n-m)位,小数部分最多m位,如(n-m)9.m9,请重新输入" );
            }
        }