1，权限的管理系统：开发项目必备的一个的功能；该项目使用 ASP.NET MVC5 SqlServer EF6 IOC容器 BoostStrap

2，登录界面验证码功能实现，整体效果如下；

3，接下来就是代码部分实现，前端页面；

 

 <div class="input-icon">
                        <i class="fa fa-lock"></i>
                        @Html.PasswordFor(m => m.CheckCode, new { @class = "form-control placeholder-no-fix", @autocomplete = "off", @placeholder = "请输入验证码" })
                        @Html.ValidationMessage("CheckCode", new { @style = "color: red" })
                    </div>
                </div>
                <div class="form-group">
                    <img style="border-radius: 7px; height: 40px;" alt="验证码图片" class="img" onclick="refresh(this)" src="/Account/VerifyCode" title="点击刷新">
                </div>

js代码在页面刷新或者点击验证码时自动生成新的验证码

 <script type="text/javascript">
        function refresh(obj) {
            $(obj).attr("src", "/Account/VerifyCode?random=" + Math.random());
        }
    </script>

4，控制器代码

  public void VerifyCode()
        {
            string code = string.Empty;
            Bitmap bitmap = VerifyCodeHelper.CreateVerifyCode(out code);
            base.HttpContext.Session["CheckCode"] = code;
            bitmap.Save(base.Response.OutputStream, ImageFormat.Gif);
            base.Response.ContentType = "image/gif";
        }

5，生成验证码的核心代码 CreateVerifyCode方法如下；

 public class VerifyCodeHelper
    {
        public static Bitmap CreateVerifyCode(out string code)
        {
            //建立Bitmap对象，绘图
            Bitmap bitmap = new Bitmap(200, 60);
            Graphics graph = Graphics.FromImage(bitmap);
            graph.FillRectangle(new SolidBrush(Color.White), 0, 0, 200, 60);
            Font font = new Font(FontFamily.GenericSerif, 48, FontStyle.Bold, GraphicsUnit.Pixel);
            Random r = new Random();
            string letters = "ABCDEFGHIJKLMNPQRSTUVWXYZ0123456789";

            StringBuilder sb = new StringBuilder();

            //添加随机的五个字母
            for (int x = 0; x < 5; x++)
            {
                string letter = letters.Substring(r.Next(0, letters.Length - 1), 1);
                sb.Append(letter);
                graph.DrawString(letter, font, new SolidBrush(Color.Black), x * 38, r.Next(0, 15));
            }
            code = sb.ToString();

            //混淆背景
            Pen linePen = new Pen(new SolidBrush(Color.Black), 2);
            for (int x = 0; x < 6; x++)
                graph.DrawLine(linePen, new Point(r.Next(0, 199), r.Next(0, 59)), new Point(r.Next(0, 199), r.Next(0, 59)));
            return bitmap;
        }
    }

以上就是实现验证码的全部，谢谢！