asp.net验证码实现

//cs页面

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.IO;
using System.Drawing.Imaging;
using System.Drawing.Drawing2D;
using System.Drawing.Printing;

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

CreateCheckCodeImage(GenerateCheckCode());
}
/// <summary>
/// 生成随机校验码字符串
/// </summary>
/// <returns>生成的随机校验码字符串</returns>
private string GenerateCheckCode()
{
int number;
string strCode = string.Empty;

//随机数种子
Random random = new Random();

for (int i = 0; i < 4; i++) //校验码长度为4
{
//随机的整数
number = random.Next();

//字符从0-9,A-Z中随机产生,对应的ASCII码分别为
//48-57,65-90
number = number % 36;
if (number < 10)
{
number += 48;
}
else
{
number += 55;
}
strCode += ((char)number).ToString();
}

//在session中保存校验码
Session["CheckCode"] = strCode;
return strCode;
}

/// <summary>
/// 根据校验码输出图片
/// </summary>
/// <param name="checkCode">产生的随机校验码</param>
private void CreateCheckCodeImage(string checkCode)
{
//若校验码为空，则直接返回
if (checkCode == null || checkCode.Trim() == String.Empty)
{
return;
}
//根据校验码的长度确定输出图片的长度
System.Drawing.Bitmap image = new System.Drawing.Bitmap(55, 20);//(int)Math.Ceiling(Convert.ToDouble(checkCode.Length * 15))
//创建Graphics对象
Graphics g = Graphics.FromImage(image);
try
{
//生成随机数种子
Random random = new Random();
//清空图片背景色
g.Clear(Color.White);
//画图片的背景噪音线 10条
//---------------------------------------------------
for (int i = 0; i < 10; i++)
{
//噪音线起点坐标(x1,y1),终点坐标(x2,y2)
int x1 = random.Next(image.Width);
int x2 = random.Next(image.Width);
int y1 = random.Next(image.Height);
int y2 = random.Next(image.Height);

//用银色画出噪音线
g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
}
//---------------------------------------------------
//Brush b = Brushes.Silver;
//g.FillRectangle(b, 0, 0, image.Width, image.Height);
//---------------------以上两种任选其一------------------------------
//输出图片中校验码的字体: 12号Arial,粗斜体
Font font = new Font("Arial", 12, (FontStyle.Bold | FontStyle.Italic));

//线性渐变画刷
LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.Purple, 1.2f, true);
g.DrawString(checkCode, font, brush, 2, 2);

//画图片的前景噪音点 50个
for (int i = 0; i < 50; i++)
{
int x = random.Next(image.Width);
int y = random.Next(image.Height);
image.SetPixel(x, y, Color.FromArgb(random.Next()));
}

//画图片的边框线
g.DrawRectangle(new Pen(Color.Peru), 0, 0, image.Width - 1, image.Height - 1);

//创建内存流用于输出图片
using (MemoryStream ms = new MemoryStream())
{
//图片格式指定为png
image.Save(ms, ImageFormat.Jpeg);
//清除缓冲区流中的所有输出
Response.ClearContent();
//输出流的HTTP MIME类型设置为"image/Png"
Response.ContentType = "image/Jpeg";
//输出图片的二进制流
Response.BinaryWrite(ms.ToArray());
}
}
finally
{
//释放Bitmap对象和Graphics对象
g.Dispose();
image.Dispose();
}
}
}
}

　　aspx页面不需要托任何控件或代码

引用验证码页面页面cs

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

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

        }

        protected void BtnLogin_Click(object sender, EventArgs e)
        {
            if (string.Compare(Session["CheckCode"].ToString(), this.TexChecknum.Text.Trim(), true) == 0)
            {
               LabCheckNum.Text = "验证码正确！";
            }
            else
            {
                LabCheckNum.Text = "验证码错误！";
            }
        }
    }
}

aspx页面

<%@ Page Title="" Language="C#" MasterPageFile="~/Site.Master" AutoEventWireup="true" CodeBehind="Login.aspx.cs" Inherits="RecruitmentSystem.Jobhunters.Login" %>
<asp:Content ID="Content1" ContentPlaceHolderID="HeadContent" runat="server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">

                <span class="style5">验证码：</span><asp:TextBox ID="TexChecknum" runat="server" 
                    Width="44px"></asp:TextBox>
    <asp:Image ID="Image1" runat="server" ImageUrl="RandomImage.aspx" Height="19px" 
                    Width="50px"/>
                <asp:LinkButton ID="LinkButtonUpdate" runat="server" CausesValidation="False">换一张</asp:LinkButton>
                <asp:RequiredFieldValidator
        ID="RequiredFieldValidator3" ControlToValidate="TexChecknum" runat="server" ErrorMessage="您还没有输入验证码"></asp:RequiredFieldValidator>
                
</asp:Content>