方法一：使用IsNullOrWhiteSpace属性 返回值为TRUE   加入！取其相反的值

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        string uname = "admin";
        string upwd = "123456";
        if (!string.IsNullOrWhiteSpace(this.TextBox1.Text) && !string.IsNullOrWhiteSpace(this.TextBox2.Text))
        {
            if (uname == this.TextBox1.Text)
            {
                if (upwd == this.TextBox2.Text)
                {
                    this.TextBox1.Text = this.TextBox2.Text = "";
                    Label1.Text = "登录成功";
                }
                else
                {
                    Label1.Text = "密码不正确";
                }
            }
            else
            {
                Label1.Text = "用户名不正确";
            }
        }
        else
        {
            Label1.Text = "用户名或密码未输入";
        }
    }
}

 

 

 

 

方法二：使用 //--利用RequiredFieldValidator 这个系统自带的验证控件进行验证，需要修改controlvalidate=text1.text 修改errormessage=提示信息