asp.net一般处理程序（.ashx）动态生成验证码案例。

{使用一般处理程序动态生成验证码}

1.新建WebSite项目，添加一般处理程序命名为  yzm.ashx，添加如下代码： 

public void ProcessRequest(HttpContext context)
    {

        //将context.Response.ContentType = "text/plain";修改为context.Response.ContentType = "image/JPEG";
        context.Response.ContentType = "image/JPEG";
        using (System.Drawing.Bitmap bitmap =
             new System.Drawing.Bitmap(150, 50))
        {
            using (System.Drawing.Graphics grapgics =
                System.Drawing.Graphics.FromImage(bitmap))
            {

                 //测试示例
                /*grapgics.DrawString("哈喽",
                   new System.Drawing.Font("宋体", 20),
                   System.Drawing.Brushes.Blue
                   , new System.Drawing.PointF(0, 0));

                System.Drawing.Pen pen = (System.Drawing.Pen)
                    System.Drawing.Pens.Red.Clone();
                pen.Width = 3;
                grapgics.DrawEllipse(pen, new System.Drawing.Rectangle(20, 20, 10, 10));

                bitmap.Save(context.Response.OutputStream,
                    System.Drawing.Imaging.ImageFormat.Jpeg);*/

                //生成随机数
                Random random = new Random();
                int code = random.Next();
                string strCode = code.ToString();

                //存session
                HttpContext.Current.Session["code"] = strCode;
                grapgics.DrawString(strCode,
                   new System.Drawing.Font("宋体", 20),
                   System.Drawing.Brushes.Blue
                   , new System.Drawing.PointF(0, 0));
                bitmap.Save(context.Response.OutputStream,
                    System.Drawing.Imaging.ImageFormat.Jpeg);

            }
        }

        //本身就有的
        context.Response.Write("Hello World");
    }

2.新建webApplication。

在<div>中添加<img src="yzm.ashx"/>

添加TextBox 和Button,Button的单击事件如下

  protected void Button1_Click(object sender, EventArgs e)
    {
        string stryzm = Convert.ToString(Session["code"]);
        if (stryzm==TextBox1.Text)
        {
            Response.Write("正确");
        }
        else
        {
            Response.Write("错误");
        }
    }

3.随后即可在WebApplication中进行测试。

原文：http://www.cnblogs.com/fanshaomin/p/3697457.html