asp.net简单生成验证码的方法

namespace WebApplication1
{ /// 
 /// $codebehindclassname$ 的摘要说明 /// 
 [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
   }  } }}