1.新建一个一般处理程序
namespace WebApplication1 { /// <summary> /// $codebehindclassname$ 的摘要说明 /// </summary> [WebService(Namespace = "http://tempuri.org/")] [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)] public class Handler1 : IHttpHandler, IRequiresSessionState { public void ProcessRequest(HttpContext context) { context.Response.ContentType = "image/gif"; //建立Bitmap对象，绘图 Bitmap basemap = new Bitmap(100, 30); Graphics graph = Graphics.FromImage(basemap); graph.FillRectangle(new SolidBrush(Color.White), 0, 0, 100, 30); Font font = new Font(FontFamily.GenericSerif, 24, FontStyle.Bold, GraphicsUnit.Pixel); Random r = new Random(); string letters = "ABCDEFGHIJKLMNPQRSTUVWXYZ"; string letter; StringBuilder s = new StringBuilder(); //添加随机的五个字母 for (int x = 0; x < 5; x++) { letter = letters.Substring(r.Next(0, letters.Length - 1), 1); s.Append(letter); graph.DrawString(letter, font, new SolidBrush(Color.Black), x * 19, r.Next(0, 8)); } //混淆背景 Pen linePen = new Pen(new SolidBrush(Color.Black), 2); for (int x = 0; x < 6; x++) graph.DrawLine(linePen, new Point(r.Next(0, 99), r.Next(0, 29)), new Point(r.Next(0, 99), r.Next(0, 29))); //将图片保存到输出流中 basemap.Save(context.Response.OutputStream, ImageFormat.Gif); context.Session["CheckCode"] = s.ToString(); //如果没有实现IRequiresSessionState，则这里会出错，也无法生成图片 context.Response.End(); } public bool IsReusable { get { return false; } } } }
2.前台代码
<html xmlns="http://www.w3.org/1999/xhtml" > <head runat="server"> <title></title> </head> <body> <form runat="server"> <div> <asp:TextBox runat="server"></asp:TextBox> <img alt="看不清？点击换一张" src="https://www.jb51.net/Handler1.ashx" /><br /> <asp:Button runat="server" Text="Button" /> </div> </form> </body> </html>