Net(C#)实现网页验证码功能

/// <summary>
 /// ValidateCode 的摘要说明。
 /// </summary>
 public class ValidateCode : System.Web.UI.Page
 {
  private void Page_Load(object sender, System.EventArgs e)
  {
   string checkCode = CreateRandomCode(4);
   Session["CheckCode"] = checkCode;
   CreateImage(checkCode);
  }
  //其中CreateRandomCode是自定义的函数，参数代表验证码位数

  private string CreateRandomCode(int codeCount)
  {
   string allChar = "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,Q,R,S,T,U,W,X,Y,Z" ;
   string[] allCharArray = allChar.Split(',');
   string randomCode = "";
   int temp = -1;

   Random rand = new Random();
   for(int i = 0; i < codeCount; i++)
   {
    if(temp != -1)
    {
     rand = new Random(i*temp*((int)DateTime.Now.Ticks));
    }
    int t = rand.Next(35);
    if(temp == t)
    {
     return CreateRandomCode(codeCount);
    }
    temp = t;
    randomCode += allCharArray[t];
   }
   return randomCode;
  }
  //CreateImage也是一个自定义的函数，用于生成图

  private void CreateImage(string checkCode)
  {
   int iwidth = (int)(checkCode.Length * 11.5);
   System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 20);
   Graphics g = Graphics.FromImage(image);
   Font f = new System.Drawing.Font("Arial", 10, System.Drawing.FontStyle.Bold);
   Brush b = new System.Drawing.SolidBrush(Color.White);
   g.FillRectangle(new System.Drawing.SolidBrush(Color.Blue),0,0,image.Width, image.Height);
   //g.Clear(Color.Blue);
   g.DrawString(checkCode, f, b, 3, 3);

   Pen blackPen = new Pen(Color.Black, 0);
   Random rand = new Random();
   for (int i=0;i<5;i++)
   {
    int y = rand.Next(image.Height);
    g.DrawLine(blackPen,0,y,image.Width,y);
   }
           
   System.IO.MemoryStream ms = new System.IO.MemoryStream();
   image.Save(ms,System.Drawing.Imaging.ImageFormat.Jpeg);
   Response.ClearContent();
   Response.ContentType = "image/Jpeg";
   Response.BinaryWrite(ms.ToArray());
   g.Dispose();
   image.Dispose();
  }

 

 调用方法:<asp:Image Runat="server" ImageUrl="ValidateCode.aspx"></asp:Image>

在新系统中已经使用