ASP.net實現驗證碼技術（網上收集)

 
第一步產生驗證碼
新增一個ValidateCode.aspx頁面
在ValidateCode.aspx.cs的代碼如下
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
{     //該頁面將用於產生驗證碼圖片
      protected void Page_Load(object sender, EventArgs e)
      {     //調用函數將驗證碼產生圖片
     this.CreateCheckCodeImage(GenerateCheckCode());
        
      }
      private string GenerateCheckCode()
      {  //產生五位的隨機字串
     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));