.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;width: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), );   //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 = ; i <= ; 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", ,(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(, , img.Width, img.Height), Color.Gray, Color.Blue, 1.4f, true);
             graphics.DrawString(ValiDateCode, font, linear, , );                        //绘制生成的验证码,
             graphics.DrawRectangle(new Pen(Color.Silver), , , img.Width - , img.Height - );
             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 = ; i <= ; i++)
             {
                 if (i %  == )
                 {
                     result.Append(letter[random.Next(, )]);
                 }
                 else
                 {
                     result.Append(random.Next(, ));
                 }
             }
             return result.ToString();
         }

效果图：