添加一般处理程序
<%@ WebHandler Language="C#" Class="yanzheng" %> using System; using System.Web; using System.Web.SessionState;//IRequiresSessionState的命名空间 using System.Drawing; public class yanzheng : IHttpHandler, IRequiresSessionState{ public void ProcessRequest (HttpContext context) { context.Response.ContentType = "image/jpeg";//要输出的类型 Bitmap img = new Bitmap(50,20);//空白图，指定大小 Graphics gr = Graphics.FromImage(img);//往哪个图上绘制 Font font = new Font("宋体",12,FontStyle.Bold);//字体样式 SolidBrush brush = new SolidBrush(Color.White);//设置画笔 gr.FillRectangle(brush,0,0,50,20);//设置画笔绘制图形的形状 brush.Color = Color.Red;//绘制图形的颜色 string s = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";//随即字符数据源 string str = ""; Random r = new Random(); for (int i = 0; i < 4; i++) { int start = r.Next(62); str += s.Substring(start,1).ToString();//取随机数，截取一位，组成4位验证码 } context.Session["yanzheng"] = str;//会话中保存 gr.DrawString(str,font,brush,0,0);//绘制图形 //保存图片，通过Response响应流保存 img.Save(context.Response.OutputStream,System.Drawing.Imaging.ImageFormat.Jpeg); } public bool IsReusable { get { return false; } } }
界面
<body> <form id="form1" runat="server" method="get"> <div> <asp:ScriptManager ID="ScriptManager1" runat="server"> </asp:ScriptManager> <br /> <asp:UpdatePanel ID="UpdatePanel1" runat="server"> <ContentTemplate> <asp:TextBox ID="txtcode" runat="server"></asp:TextBox> <asp:ImageButton ID="ImageButton1" runat="server" ImageUrl="yanzheng.ashx" OnClick="ImageButton1_Click" /> <br /> <asp:Button ID="btn_checkCode" runat="server" OnClick="btn_checkCode_Click" Text="验证" /> <br /> <asp:Label ID="Label1" runat="server"></asp:Label> </ContentTemplate> </asp:UpdatePanel> </div> </form> </body>
protected void ImageButton1_Click(object sender, ImageClickEventArgs e) { ImageButton1.ImageUrl = "yanzheng.ashx?id="+new Random().Next(100); } protected void btn_checkCode_Click(object sender, EventArgs e) { string s1 = txtcode.Text.ToUpper(); string s2 = Session["yanzheng"].ToString().ToUpper(); if (s1==s2) { Label1.Text = "验证成功"; } else { Response.Write("<script>alert(‘验证失败‘)</script>"); } }
原文：http://www.cnblogs.com/happinesshappy/p/4662929.html