限制只能輸入數字

        //限制只能輸入數字------------------------------------------------------
        private void txtUserID_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyChar != '\b' && !Char.IsDigit(e.KeyChar))
            {
                e.Handled = true;
                MessageBox.Show("請輸入數字，並確保在11位以內！");
            }
        }
 

限制只能輸入字母和數字

        //限制密碼只能輸入字母或者數字
        private void txtPassword_KeyPress(object sender, KeyPressEventArgs e)
        {
            if ((e.KeyChar >= 'a' && e.KeyChar <= 'z') || (e.KeyChar >= 'A' && e.KeyChar <= 'Z')
    || (e.KeyChar >= '0' && e.KeyChar <= '9') || (e.KeyChar == 8))
            {
                e.Handled = false;

            }
            else
            {
                e.Handled = true;
                MessageBox.Show("密碼只能是字母或者數字");
            }
        }
 

限制只能輸入漢字

        //新增名稱空間
        using System.Text.RegularExpressions;        


        //限制只能輸入漢字
        private void txtSName_KeyPress(object sender, KeyPressEventArgs e)
        {
            Regex rg = new Regex("^[\u4e00-\u9fa5\b]$"); //\b是退格鍵
            if (!rg.IsMatch(e.KeyChar.ToString()))
            {
                e.Handled = true;
                MessageBox.Show("您只能輸入漢字！");
            }
        }