webform 验证码

在webform中写验证码必须先建一个一般处理程序。

public class Handler : IHttpHandler ,IRequiresSessionState//session接口
{
    
    public void ProcessRequest (HttpContext context) {
            context.Response.ContentType = "image/Jpeg";
           
                string charSet = "2,3,4,5,6,8,9,A,B,C,D,E,F,G,H,J,K,M,N,P,R,S,U,W,X,Y";
                string[] CharArray = charSet.Split(',');    
                string code = "";       
                int temp = -1;       
                Random rand1 = new Random();      
                for (int j = 0; j < 4; j++)       
                {         
                    if (temp != -1)    
                    {            
                        rand1 = new Random(j * temp * ((int)DateTime.Now.Ticks)); 
                    }            
                    int t = rand1.Next(CharArray.Length - 1);   
                    if (temp == t)            
                    {          
                        return;         
                    }            
                    temp = t;         
                    code += CharArray[t];   
                }             
            context.Session["yanzhen"]=code;
            System.Drawing.Bitmap image = new System.Drawing.Bitmap(50, 23);
            Graphics g = Graphics.FromImage(image);
            Font f = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Italic | System.Drawing.FontStyle.Bold));        // 前景色  

            Brush b = new System.Drawing.SolidBrush(Color.Black);        // 背景色       
            g.Clear(Color.White);        // 填充文字        
            g.DrawString(code, f, b, 0, 1);        // 随机线条        
            Pen linePen = new Pen(Color.Gray, 0);
            Random rand = new Random();
            for (int i = 0; i < 5; i++)
            {
                int x1 = rand.Next(image.Width);
                int y1 = rand.Next(image.Height);
                int x2 = rand.Next(image.Width);
                int y2 = rand.Next(image.Height);
                g.DrawLine(linePen, x1, y1, x2, y2);
            }
            // 随机点        
            for (int i = 0; i < 30; i++)
            {
                int x = rand.Next(image.Width);
                int y = rand.Next(image.Height);
                image.SetPixel(x, y, Color.Gray);
            }
            // 边框       
            g.DrawRectangle(new Pen(Color.Gray), 0, 0, image.Width - 1, image.Height - 1);
            // 输出图片  
            System.IO.MemoryStream ms = new System.IO.MemoryStream();
            image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
            context.Response.ClearContent();        
            context.Response.BinaryWrite(ms.ToArray()); 
    }

再用简单的ajax异步操作刷新

function ajax(url,success) {
    var xmlrequest = window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject('Microsoft.XMLHTTP');
    xmlrequest.open("POST", url, true);
    xmlrequest.onreadystatechange() = function () {
        if (xmlrequest.readyState==4) {
            if (xmlrequest.status == 200) {
                success(xmlrequest.responseText);
            }
            else {
                alert("Action错误！");
            }
        }
    }
    xmlrequest.send();
}