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),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 ); } //g.FillRectangle new System.Drawing.SolidBrush Color.Blue),0,0,image.Width, image.Height); g.Clear Color.Blue);

这两种方法都可以改变生成图片的背景颜色
下面那个for循环用来生成一些随机的水平线

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>