ASP.NET中生成验证码（C#）

首先在登陆界面login.aspx加一个Image控件，ImageUrl指向ValidateCode.aspx。

ValidateCode.aspx用来生成验证码。Page_Load如下：

private void Page_Load(object sender, System.EventArgs e)

{

string checkCode = CreateRandomCode(4);

Session["CheckCode"] = checkCode;

CreateImage(checkCode);

}

其中定义了两个函数，CreateRandomCode生成验证码，CreateImage将其输入到页面。对于用Session记录验证码，当然是用于判断验证码的输入是否正确了。

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", 10, System.Drawing.FontStyle.Bold);

Brush b = new System.Drawing.SolidBrush(Color.DarkBlue);

g.Clear(Color.White);

g.DrawString(checkCode, f, b, 3, 3);

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();

}