1 protected void Page_Load(object sender, EventArgs e)2 {3 string tmp = RndNum(4);4 HttpCookie a = new HttpCookie("ImageV", tmp);5 Response.Cookies.Add(a);6 this.ValidateCode(tmp);7 }8 private void ValidateCode(string VNum)9 {10 Bitmap Img = null;11 Graphics g = null;12 MemoryStream ms = null;1314 int gheight = VNum.Length * 12;15 Img = new Bitmap(gheight, 25);16 g = Graphics.FromImage(Img);17 //背景颜色18 g.Clear(Color.LightSteelBlue);19 //文字字体20 Font f = new Font("Arial Black", 10);21 //文字颜色22 SolidBrush s = new SolidBrush(Color.RoyalBlue);23 g.DrawString(VNum, f, s, 3, 3);24 ms = new MemoryStream();25 Img.Save(ms, ImageFormat.Jpeg);26 Response.ClearContent();27 Response.ContentType = "images/Jpeg";28 Response.BinaryWrite(ms.ToArray());29 g.Dispose();30 Img.Dispose();31 Response.End();32 }3334 private string RndNum(int VcodeNum)35 {36 string Vchar = "0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p" +37 ",q,r,s,t,u,v,w,x,y,z";38 string VcArray = Vchar.Split(new Char { '','' });39 string VNum = "";40 int temp = -1;4142 Random rand = new Random();4344 for (int i = 1; i < VcodeNum + 1; i++)45 {46 if (temp != -1)47 {48 rand = new Random(i * temp * unchecked((int)DateTime.Now.Ticks));49 }5051 int t = rand.Next(35);52 if (temp != -1 && temp == t)53 {54 return RndNum(VcodeNum);55 }56 temp = t;57 VNum += VcArray[t];58 }59 return VNum;60 } 使用方法：
在需要它的页面html里添加
<img src="identifyingcode.aspx" />
HttpCookieCollection cookies = Request.Cookies;
string tmp = cookies["ImageV"].Value;
然后比tmp与获取的较验证码文本框中的值是否相同