ASP.NET实现验证码以及刷新验证码的小例子

实现代码

/// <summary>    /// 生成验证码图片，保存session名称VerificationCode    /// </summary>    public static void CreateVerificationCode()    {        int number;        string checkCode = string.Empty;        //随机数种子        Random randoms = new Random();        for (int i = 0; i < 4; i++) //校验码长度为4        {            //随机的整数            number = randoms.Next();            //字符从0-9,A-Z中随机产生,对应的ASCII码分别为            //48-57,65-90            number = number % 36;            if (number < 10)            {                number += 48;            }            else            {                number += 55;            }            checkCode += ((char)number).ToString();        }        //在session中保存校验码        System.Web.HttpContext.Current.Session["VerificationCode"] = checkCode;        //若校验码为空，则直接返回        if (checkCode == null || checkCode.Trim() == String.Empty)        {            return;        }        //根据校验码的长度确定输出图片的长度        System.Drawing.Bitmap image = new System.Drawing.Bitmap(55, 20);//(int)Math.Ceiling(Convert.ToDouble(checkCode.Length * 15))        //创建Graphics对象        Graphics g = Graphics.FromImage(image);        try        {            //生成随机数种子            Random random = new Random();            //清空图片背景色            g.Clear(Color.White);            //画图片的背景噪音线 10条            //---------------------------------------------------            for (int i = 0; i < 10; i++)            {                //噪音线起点坐标(x1,y1),终点坐标(x2,y2)                int x1 = random.Next(image.Width);                int x2 = random.Next(image.Width);                int<span>本文来源gaodai#ma#com搞*!代#%^码$网*</span> y1 = random.Next(image.Height);                int y2 = random.Next(image.Height);                //用银色画出噪音线                g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);            }            //---------------------------------------------------            //Brush b = Brushes.Silver;            //g.FillRectangle(b, 0, 0, image.Width, image.Height);            //---------------------以上两种任选其一------------------------------            //输出图片中校验码的字体: 12号Arial,粗斜体            Font font = new Font("Arial", 12, (FontStyle.Bold | FontStyle.Italic));            //线性渐变画刷            LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.Purple, 1.2f, true);            g.DrawString(checkCode, font, brush, 2, 2);            //画图片的前景噪音点 50个            for (int i = 0; i < 50; i++)            {                int x = random.Next(image.Width);                int y = random.Next(image.Height);                image.SetPixel(x, y, Color.FromArgb(random.Next()));            }            //画图片的边框线            g.DrawRectangle(new Pen(Color.Peru), 0, 0, image.Width - 1, image.Height - 1);            //创建内存流用于输出图片            using (MemoryStream ms = new MemoryStream())            {                //图片格式指定为png                image.Save(ms, ImageFormat.Jpeg);                //清除缓冲区流中的所有输出                System.Web.HttpContext.Current.Response.ClearContent();                //输出流的HTTP MIME类型设置为"image/Png"                System.Web.HttpContext.Current.Response.ContentType = "image/Jpeg";                //输出图片的二进制流                System.Web.HttpContext.Current.Response.BinaryWrite(ms.ToArray());            }        }        finally        {            //释放Bitmap对象和Graphics对象            g.Dispose();            image.Dispose();        }    }

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