验证控件CustomValidator的用法(自定义错误控件--连实据库Vote库)

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;

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

    }
    protected void CustomValidator1_ServerValidate(object source, ServerValidateEventArgs args)
    {
        //获取CustomValidator控件绑定文本框的值
        string userName=args.Value;
        //连接数据库
        SqlConnection con = new SqlConnection("server=.;database=Vote;uid=sa;pwd=;");
        con.Open();
        //查询所有符合条件的记录数
        SqlCommand cmd = new SqlCommand("select count(*) from VoteDetails where VoteItem='" + userName + "'", con);
        //返回查询条件的首行首列
        int count =Convert.ToInt32( cmd.ExecuteScalar());
        //如果没有找到
        if (count == 0)
        {
            //则通过验证,不显示CustomValidator控件的错误信息
            args.IsValid = true;
        }
        else
        {
            //否则不能通过验证,显示错误信息,用户以存在
            args.IsValid = false;
        }
        //记住关闭数据库
        //除了CustomValidator是服务器验证控件,其他的基本上多是客户端验证控件
        con.Close();
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        //页面的全部数据有效则执行下列代码
        if (this.IsValid)
        {
            Response.Write("提交");
        }
        else
        {
            Response.Write("页面无效");
        }
    }
}