它的后台cs文件代码如下：
PageLoad
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),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);
在需要用到验证码的页面添加一个<asp:Image>控件即可，但是要把ImageUrl指向生成验证码的页面
<asp:Image Runat="server" ID="ImageCheck" ImageUrl="ValidateCode.aspx"></asp:Image>
