asp.net添加验证码

1.新建一个aspx页面生成验证码图像

using System;

using System.Data;

using System.Configuration;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

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;

public partial class NewWeb_CheckCode : System.Web.UI.Page

{

    protected void Page_Load(object sender, EventArgs e)

    {

        CreateCheckCodeImage(GenerateCheckCode());

    }

    private string GenerateCheckCode()

    {

        int number;

        char code;

        string checkCode = String.Empty;

        System.Random random = new Random();

        for (int i = ; i < ; i++)

        {

            number = random.Next();

            if (number %  == )

                code = (char)('' + (char)(number % ));

            else

                code = (char)('A' + (char)(number % ));

            checkCode += code.ToString();

        }

        //Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));

        Session["M2CheckCode"] = checkCode;

        return checkCode;

    }

    private void CreateCheckCodeImage(string checkCode)

    {

        if (checkCode == null || checkCode.Trim() == String.Empty)

            return;

        System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), );

        Graphics g = Graphics.FromImage(image);

        try

        {

            //生成随机生成器

            Random random = new Random();

            //清空图片背景色

            g.Clear(Color.White);

            //画图片的背景噪音线

            for (int i = ; i < ; i++)

            {

                int x1 = random.Next(image.Width);

                int x2 = random.Next(image.Width);

                int y1 = random.Next(image.Height);

                int y2 = random.Next(image.Height);

                g.DrawLine(new Pen(Color.Black), x1, y1, x2, y2);

            }

            Font font = new System.Drawing.Font("Arial", , (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));

            System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(, , image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);

            g.DrawString(checkCode, font, brush, , );

            //画图片的前景噪音点

            for (int i = ; i < ; 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.Silver), , , image.Width - , image.Height - );

            System.IO.MemoryStream ms = new System.IO.MemoryStream();

            image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);

            Response.ClearContent();

            Response.ContentType = "image/Gif";

            Response.BinaryWrite(ms.ToArray());

        }

        finally

        {

            g.Dispose();

            image.Dispose();

        }

    }

}

2.在添加验证码的地方添加

<img id="ImgCheckCode" alt="验证码" src="CheckCode.aspx" onclick="reloadcode();" style="cursor:pointer;" />

 //验证码刷新

 function reloadcode() {

     document.getElementById("ImgCheckCode").src = "CheckCode.aspx?a=" + Math.random();

 }