Asp.net(C#)实现验证码功能代码

private void Page_Load(object sender,System.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 * ((@R_262_10185@datetiR_860_11845@e.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 = (@R_262_10185@(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),image.Width,image.Height);
g.Clear(Color.bluE);
g.DrawString(checkCode,f,b,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,y,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();
}
//g.FillRectangle(new System.Drawing.SolidBrush(Color.bluE),image.Height);
g.Clear(Color.bluE);

<asp:Image Runat="server" ID="Imagecheck" ImageUrl="ValidateCode.aspx"></asp:Image>