.net生成随机验证码图片

private string GenerateCheckCode()

    {<br/>
        int number;<br/>
        string strCode = string.Empty;<br/>
        //随机种子<br/>
        //Random random = new Random();<br/>
        //for (int i = 0; i &lt; 4; i++) //验证码长度为4<br/>
        //{<br/>
        //    //随机整数<br/>
        //    number = random.Next();<br/>
        //    //字符从0-9，A-Z中产生，对应的ASCII码为48-57，65-90<br/>
        //    number = number % 36;<br/>
        //    if (number &lt; 10)<br/>
        //    {<br/>
        //        number += 48;<br/>
        //    }<br/>
        //    else<br/>
        //    {<br/>
        //        number += 55;<br/>
        //    }<br/>
        //    strCode += ((char)number).ToString();<br/>
        //}

//产生随机字符串

        strCode =  GenCode();

//将字符串保存在Cookies

        Response.Cookies.Add(new HttpCookie(&#34;gst_checkCode&#34;, strCode));<br/>
        return strCode;

} private string GenCode(int num)

    {<br/>
        string[] source ={&#34;&#34;,&#34;&#34;,&#34;&#34;,&#34;&#34;,&#34;&#34;,&#34;&#34;,&#34;&#34;,&#34;&#34;,&#34;&#34;,&#34;&#34;,<br/>
                            &#34;A&#34;,&#34;B&#34;,&#34;C&#34;,&#34;D&#34;,&#34;E&#34;,&#34;F&#34;,&#34;G&#34;,&#34;H&#34;,&#34;i&#34;,&#34;J&#34;,&#34;K&#34;,&#34;L&#34;,&#34;M&#34;,&#34;N&#34;,<br/>
                            &#34;o&#34;,&#34;P&#34;,&#34;Q&#34;,&#34;R&#34;,&#34;S&#34;,&#34;T&#34;,&#34;U&#34;,&#34;V&#34;,&#34;W&#34;,&#34;X&#34;,&#34;Y&#34;,&#34;Z&#34;};<br/>
        string code = &#34;&#34;;<br/>
        Random rd = new Random();<br/>
        for (int i = ; i &lt; num; i++)<br/>
        {<br/>
            code += source[rd.Next(, source.Length)];<br/>
        }<br/>
        return code;<br/>
    }

//生成图片

    private void CreateCheckCodeImage(string checkCode)<br/>
    {<br/>
        //若检验码为空，则直接返回<br/>
        if (checkCode == null || checkCode.Trim() == string.Empty)<br/>
            return;<br/>
        //根据验证码长度确定输出图片的长度<br/>
        System.Drawing.Bitmap image = new Bitmap((int)Math.Ceiling(float.Parse((checkCode.Length * ).ToString())), );

//创建Graphics对象

        System.Drawing.Graphics g = Graphics.FromImage(image);

//生成随机数种子

        Random random = new Random();<br/>
        //清除图片背景颜色<br/>
        g.Clear(Color.White);<br/>
        //画背景图片的噪音线10条<br/>
        for (int i = ; i &lt; ; i++)<br/>
        {<br/>
            //噪音线起点坐标(x1,y1),终点坐标(x2,y2)<br/>
            int x1 = random.Next(image.Width);<br/>
            int x2 = random.Next(image.Width);<br/>
            int y1 = random.Next(image.Height);<br/>
            int y2 = random.Next(image.Height);<br/>
            //用银色线画出噪音线<br/>
            g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);<br/>
        }<br/>
        //输出图片中校验码的字体:12号Arial,粗斜体<br/>
        Font font = new Font(&#34;Arial&#34;, , FontStyle.Bold);<br/>
        //线性渐变画刷<br/>
        System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(, , image.Width, image.Width), Color.Blue, Color.Purple, 1.2f, true);<br/>
        g.DrawString(checkCode, font, brush, , );<br/>
        //画图片的前景噪点50个<br/>
        for (int i = ; i &lt; ; i++)<br/>
        {<br/>
            int x = random.Next(image.Width);<br/>
            int y = random.Next(image.Height);<br/>
            image.SetPixel(x, y, Color.FromArgb(random.Next()));<br/>
        }<br/>
        //画图片段边框线<br/>
        g.DrawRectangle(new Pen(Color.SaddleBrown), , , image.Width - , image.Height - );<br/>
        //创建内存流用于输出图片<br/>
        System.IO.MemoryStream ms = new System.IO.MemoryStream();<br/>
        //图片格式指定为png<br/>
        image.Save(ms, System.Drawing.Imaging.ImageFormat.Png);

//清除缓冲区流中的所有输出

        Response.ClearContent();<br/>
        //输出流的Http Mime类型设置为&#34;image/Png&#34;<br/>
        Response.ContentType = &#34;image/Png&#34;;<br/>
        //输出图片的二进制流<br/>
        Response.BinaryWrite(ms.ToArray()); 

//释放Bitmap和Graphics对象

        g.Dispose();<br/>
        image.Dispose();<br/>
    }