通过c#生成验证码的步骤

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Text;
using System.Drawing;

public partial class checkcode : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
string checkCode = CreateRandomCode(4);
Session["CheckCode"] = checkCode;
CreateImage(checkCode);

}
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;
}
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", 8, System.Drawing.FontStyle.Regular);
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();
}
}