asp.net写验证码

生成验证码与匹配验证码的服务端代码

<%@ WebHandler Language="C#" Class="ValidataeCodeHandler" %>

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

public class ValidataeCodeHandler : IHttpHandler, System.Web.SessionState.IRequiresSessionState
{

    public void ProcessRequest(HttpContext context)
    {
        //请求类型：获取验证码图片，匹配验证码
        string type = context.Request["type"];

        if (type == "math")
        {
            if (string.IsNullOrEmpty(context.Request["code"]))
                context.Response.Write();
            else if (string.IsNullOrEmpty("" + context.Session["yqcode" + context.Request["id"]]))
            {
                context.Response.Write();
            }
            else
            {
                if ("" + context.Session["yqcode" + context.Request["id"]] == context.Request["code"] + "")
                    context.Response.Write();
                else
                    context.Response.Write();

            }
        }
        else
        {
            context.Response.ContentType = "image/gif";

            string validateCode = CreateValidateCode(context);//生成验证码
            Bitmap bitmap = new Bitmap(imgWidth, imgHeight);//生成Bitmap图像
            DisturbBitmap(bitmap); //图像背景
            DrewValidateCode(bitmap, validateCode);//绘制验证码图像
            bitmap.Save(context.Response.OutputStream, ImageFormat.Gif);//保存图像，等待输出 

            context.Response.Write(bitmap);
        }
    }

    //  private int codeLen = 4;//验证码长度
    private int fineness = ;//图片清晰度
    private int imgWidth = ;//图片宽度
    private int imgHeight = ;//图片高度
    private string fontFamily = "Times New Roman";//字体名称
    private int fontSize = ;//字体大小
    //private int fontStyle = 0;//字体样式
    private int posX = ;//绘制起始坐标X
    private int posY = ;//绘制坐标Y
    private string CreateValidateCode(HttpContext context) //生成验证码
    {
        string validateCode = "";
        Random random = new Random();// 随机数对象
        validateCode = random.Next(, ) + "";
        //for (int i = 0; i < codeLen; i++)//循环生成每位数值
        //{
        //    int n = random.Next(10);//数字
        //    validateCode += n.ToString();
        //}
        context.Session["yqcode" + context.Request["id"]] = validateCode;//保存验证码 这Session是在前台调用的。
        return validateCode;// 返回验证码
    }

    private void DisturbBitmap(Bitmap bitmap)//图像背景
    {
        Random random = new Random();//通过随机数生成
        for (int i = ; i < bitmap.Width; i++)//通过循环嵌套，逐个像素点生成
        {
            for (int j = ; j < bitmap.Height; j++)
            {
                if (random.Next() <= this.fineness)
                    bitmap.SetPixel(i, j, Color.LightGray);
            }
        }
    }
    private void DrewValidateCode(Bitmap bitmap, string validateCode)//绘制验证码图像
    {
        Graphics g = Graphics.FromImage(bitmap);//获取绘制器对象
        Font font = new Font(fontFamily, fontSize, FontStyle.Bold);//设置绘制字体
        g.DrawString(validateCode, font, Brushes.Black, posX, posY);//绘制验证码图像
    }

    public bool IsReusable
    {
        get
        {
            return false;
        }
    }

}

手动刷新验证码

<script type="text/javascript">
         //点击刷新验证码
         function f_refreshtype() {
             var Image1 = document.getElementById("valiCode");
             if (Image1 != null) {
                 Image1.src = Image1.src + "?";
             }
         }
     </script>

提交表单前ajax同步验证验证码是否正确

var urlCode = '/Handler/ValidataeCodeHandler.ashx?id=12&type=math&code=' + $.trim($("#yzcode").val());
        //ajax同步请求
        var mathresult = $.ajax({ type: "GET", url: urlCode, async: false }).responseText;
        if (mathresult != 1) {
            var Image1 = document.getElementById("valiCode");
            if (Image1 != null) {
                Image1.src = Image1.src + "?";
        }
        alert("验证码不匹配！");
        return false;
  }  

<div class="line">
  <span>验证码：</span><input value="" type="text" name="yzcode" id="yzcode" class="tong" />
  <em><img id="valiCode" name="valiCode" onclick="f_refreshtype();" style="height:32px;" src="/Handler/ValidataeCodeHandler.ashx?id=12"/></em>
</div>