ASP.NET验证码生成与验证

ASP.NET字母加数字验证码，纯字母和纯数字验证码的生成以及利用Session验证

演示地址：http://www.pengyaou.com/ValidateCodeHandler.aspx

原文出处：http://www.pengyaou.com/LegendsZ/File/2014/08/21/20140821092249684.html

 public  string NumAndLetter(int type)  
        {  
            //定义一个包括数字、大写英文字母和小写英文字母的字符串  
            string strchar = "";  
  
            switch (type)  
            {  
                case 0:  
                    strchar = "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,V,W,X,Y,Z";  
                    break;  
                case 1:  
                    strchar = "0,1,2,3,4,5,6,7,8,9";  
                    break;  
                case 2:  
                    strchar = "A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z";  
                    break;  
            }  
  
            //将strchar字符串转化为数组  
  
            string[] VcArray = strchar.Split(',');  
  
            string validateCode = "";  
  
            //采用一个简单的算法以保证生成的随机数不同  
            Random rand = new Random();  
            //验证码长度  
            for (int i = 1; i < 5 ; i  )  
            {  
  
                int t = rand.Next(VcArray.Length);  
  
                validateCode  = VcArray[t];  
            }  
  
            Session["validatecode"] = validateCode.ToUpper();//可将其保存在Session中  
            
            return validateCode; //返回生成的随机数  
        }  
  
        private  void DisturbBitmap(Bitmap bitmap)//图象背景  
        {  
            Random random = new Random();  
            for (int i = 0; i < bitmap.Width; i  )  
            {  
                for (int j = 0; j < bitmap.Height; j  )  
                {  
                    if (random.Next(100) <= 100)  
                        bitmap.SetPixel(i, j, Color.DarkGreen);  
                }  
            }  
        }  
        private  string DrawValidateCode(Bitmap bitmap, string validateCode)//绘制验证码图像  
        {  
            Graphics g = Graphics.FromImage(bitmap);  
  
            Font font = new Font("微软雅黑", 14, FontStyle.Bold);  
  
            g.DrawString(validateCode, font, Brushes.White, 10, 0);  
  
            System.Drawing.Image mImage = new Bitmap(70, 30);  
  
            g.DrawImage(bitmap, new Rectangle(0, 0, 64, 30));  
  
            string id = DateTime.Now.ToString("yyyyMMddHHmmssfff");  
  
            string path = System.Web.HttpContext.Current.Server.MapPath("Validate/" id ".jpg");  
  
            bitmap.Save(path, System.Drawing.Imaging.ImageFormat.Jpeg);  
  
            return "Validate/" id ".jpg";  
        }  
  
        public string VC(string str)  
        {  
            string returnString = "";  
  
  
            if (str == strs)  
                returnString = "1";  
  
            returnString = "0";  
  
            return returnString;  
        }