C#验证码

生成验证码

1、由字母和数字组成固定长度随机字符串 

//得到随机字符串,长度暂限定为4        private string getRandomValidate()        {            int num;            int tem;            string rtuStr = "";            for (int i = 0; i < 2; i++)            {                num = ran.Next();                tem = num % 10 + '0';//生成数字                rtuStr += Convert.ToChar(tem).ToString();                num = ran.Next();                tem = num % 26 + 'A';//生成字符                rtuStr += Convert.ToChar(tem).ToString();            }            return rtuStr;        }

2、对所生成的字符串进行绘画、同时向画上画干扰线等

//生成图像        private void getImageValidate(string strValue)        {            //string str=oo00;前两个为字母o，后两个数为0             int width = Convert.ToInt32(strValue.Length * 20);            Bitmap img = new Bitmap(width, 30);            Graphics gfc = Graphics.FromImage(img);            gfc.Clear(Color.White);            drawLine(gfc, img);            //写验证码，要定义Font            Font font = new Font("arial", 18, FontStyle.Bold);            //Font font = new Font("宋体",12,FontStyle.Bold|FontStyle.Italic);            System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, img.Width, img.Height), Color.DarkOrchid, Color.Black, 1.5f, true);            gfc.DrawString(strValue, font, brush, 3, 2);            drawPoint(img);            gfc.DrawRectangle(new Pen(Color.DarkBlue), 0, 0, img.Width - 1, img.Height - 1);            //将图像添加到页面            MemoryStream ms = new MemoryStream();            img.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);            //更改HTTP            Response.ClearContent();            Response.ContentType = "image/gif";            Response.BinaryWrite(ms.ToArray());            //Dispose            gfc.Dispose();            img.Dispose();            Response.End();        }

//划线        private void drawLine(Graphics gfc, Bitmap img)        {            //选择画10条线，也可以增加，也可以不要线，只要随机杂点就行            for (int i = 0; i < 10; i++)            {                int x1 = ran.Next(img.Width);                int y1 = ran.Next(img.Height);                int x2 = ran.Next(img.Width);                int y2 = ran.Next(img.Height);                gfc.DrawLine(new Pen(Color.Cyan), x1, y1, x2, y2);//注意画笔要淡，不然看不清            }        }

//画点        private void drawPoint(Bitmap img)        {            int col = ran.Next();//在一次的图片中杂点颜色相同            for (int i = 0; i < 100; i++)            {                int x = ran.Next(img.Width);                int y = ran.Next(img.Height);                img.SetPixel(x, y, Color.FromArgb(col));            }        }

3、将所生成的验证码字符串写入Session或Cookie中以便验证

            string str= getRandomValidate();            Session["CheckCode"] = str;

4、在验证码显示处讲img标签的src属性设为生成验证码的页面

<img id="code" src="AdminCode.aspx" alt="" width="80" height="40" ondblclick="refreshCode()"/>

5、js刷新验证码时需将img标签的src属性设置为页面+随机数形式，如：code.aspx？New Date().getTime();以保证清空缓存每次都重新加载验证码达到刷新效果

<script type="text/javascript">        function refreshCode() {            $("#code").attr("src", "AdminCode.aspx?"+new Date().getTime());        }    </script>