.Net (MVC) 随机生成验证码

   以前一直对C#的GDI画图部分知识点不怎么用所以忘得差不多了，这两天正好公司要做一个博客系统，其中一个需求就是留言时为了防止恶意攻击必须填写验证码，正好借着这个机会复习了一下，以下是实现代码，写的比较简单。

View 层

@{
    ViewBag.Title = "Home Page";
} 
<div class="row">
     <h1>test</h1>
    <div class="col-lg-12">
        @using(Html.BeginForm("Index","Home", FormMethod.Post, new {@id="form",@enctype = "multipart/form-data" }))
        {
            <div class="form-group">
                <input type="file" name="file"/>
                <input type="file" name="files" />
                <button>提交</button>
            </div>
            <div class="form-group">
                <div class="col-lg-1">
                    <input type="text" class="col-lg-3"/>
                </div>
                <div class="col-lg-3">
                    <img id="img" onclick="CheckCode()" src="/Home/GetValidateCode" style="height:30px;110px" title="点击更换" alt="点击更换" />
                    <a href="javascript:void(0)" onclick="CheckCode()">点击更换</a>
                </div>
            </div>
        }
    </div>
</div>
@section scripts{
<script>
    $(function () { 
        $("#img").click(function () {
            CheckCode()
        })
    })
    function CheckCode() {
        $("#img").attr("src", "/Home/GetValidateCode?date="+new Date());
    }
     
</script>
}

Controller 层 

/// <summary>
        /// View页面请求获得验证码
        /// </summary>
        public void GetValidateCode()
        {
            //获取随机生成的编码
            string ValiDateCode = GetValiDateCode();
            Session["Key"] = ValiDateCode;
            byte[] bytes = GetValidateCode(ValiDateCode);
            Response.ClearContent();
            Response.ContentType = "image/Gif";
            Response.BinaryWrite(bytes);
            // 也可以用MVC 的FileResult 
            //return File(bytes, @"image/jpeg");
        }

        /// <summary>
        /// 生成验证码方法
        /// </summary>
        /// <param name="ValiDateCode"></param>
        /// <returns></returns>
        public static byte[] GetValidateCode(string ValiDateCode)
        { 
            Bitmap img = new Bitmap((int)Math.Ceiling(ValiDateCode.Length * 12.6), 22);   //创建 Bitmap对象 
            Graphics graphics = Graphics.FromImage(img);                                  //创建 Graphics 对象 
            graphics.Clear(Color.White);                                                  //清空图片背景色
            Random random = new Random();                                                 //创建 Random 实例
            for (int i = 0; i <= 24; i++)
            {
                int x1 = random.Next(img.Width);
                int x2 = random.Next(img.Width);
                int y1 = random.Next(img.Height);
                int y2 = random.Next(img.Height);
                graphics.DrawLine(new Pen(Color.Silver),x1, y1, x2, y2);                  //在图片上画噪点线
            }
            Font font = new Font("Arial", 13,(FontStyle.Bold));
            //创建 Brush 对象, LinearGradientBrush实现字体渐变效果  LinearGradientBrush(Rectangle rectangle,Color color1,Color color2,float angle, bool isAngleScaleable)                                
            LinearGradientBrush linear = new LinearGradientBrush(new Rectangle(0, 0, img.Width, img.Height), Color.Gray, Color.Blue, 1.4f, true);
            graphics.DrawString(ValiDateCode, font, linear, 2, 2);                        //绘制生成的验证码,
            graphics.DrawRectangle(new Pen(Color.Silver), 0, 0, img.Width - 1, img.Height - 1);
            MemoryStream stream = new MemoryStream();                                     //创建 流对象
            img.Save(stream, ImageFormat.Jpeg);                                           //将图像以特定的格式保存到流对象中
            return stream.ToArray();
        }

        /// <summary>
        /// 获取随机生成的验证码
        /// </summary>
        /// <returns></returns>
        private static string GetValiDateCode()
        {
            string[] letter = new string[] { "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "i", "m", "n", "o", "p", "Q" };
            Random random = new Random();
            StringBuilder result = new StringBuilder();
            for (int i = 1; i <= 5; i++)
            {
                if (i % 2 == 0)
                {
                    result.Append(letter[random.Next(1, 15)]);
                }
                else
                {
                    result.Append(random.Next(1, 9));
                }
            }
            return result.ToString();
        }

效果图：