ASP.net实现验证码技术（网上收集)

 
第一步生成验证码
新增一个ValidateCode.aspx页面
在ValidateCode.aspx.cs的代码如下
using System;
using System.Data;
using System.Configuration;
using System.Collections;
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.Drawing;
using System.Drawing.Imaging;
public partial class ValidateCode : System.Web.UI.Page
{     //该页面将用于生成验证码图片
      protected void Page_Load(object sender, EventArgs e)
      {     //调用函数将验证码生成图片
     this.CreateCheckCodeImage(GenerateCheckCode());
        
      }
      private string GenerateCheckCode()
      {  //产生五位的随机字符串
     int number;
     char code;
     string checkCode = String.Empty;
     System.Random random = new Random();
     for (int i = 0; i < 5; i++)
     {
         number = random.Next();
         if (number % 2 == 0)
             code = (char)('0' + (char)(number % 10));