app_code文件夹类无法访问Web项目文件夹

Question

我有一个用于批量电子邮件服务的Web应用程序。现在，某些表格可以访问我的其他文件夹，其中包含用于发送电子邮件的图像。根文件夹mail1.aspx可以从Web peoject文件夹图像访问图像。我的app_code文件夹为何无法访问此图像文件，但出现对象引用错误。

这是我的app_code文件代码：

if (fbody.Contains("src='cid:"))
        {
            var htmlView = AlternateView.CreateAlternateViewFromString(msg.Body, null, "text/html");
            do
            {
                int src = fbody.IndexOf("src='cid:");
                if (src != -1)
                {
                    fbody = fbody.Remove(0, src + 9);
                    var dot = Regex.Match(fbody, @"\.(jpg|jpeg|gif|png)");
                    if (dot.Success)
                    {
                        int comma = fbody.IndexOf("'");
                        if (comma != -1)
                        {
                            if (!string.IsNullOrEmpty(fbody.Substring(0, comma)))
                            {
                                string imageSource = (HttpContext.Current.Server.MapPath("~/EmailImages/") + fbody.Substring(0, comma));
                                var leftImageLink = (dynamic)null;
                                switch (Path.GetExtension(imageSource).ToLower())
                                {
                                    case ".jpg":
                                        leftImageLink = new LinkedResource(imageSource, "image/jpg")
                                        {
                                            ContentId = fbody.Substring(0, comma),
                                            TransferEncoding = System.Net.Mime.TransferEncoding.Base64
                                        };
                                        break;
                                    case ".jpeg":
                                        leftImageLink = new LinkedResource(imageSource, "image/jpeg")
                                        {
                                            ContentId = fbody.Substring(0, comma),
                                            TransferEncoding = System.Net.Mime.TransferEncoding.Base64
                                        };
                                        break;
                                    case ".gif":
                                        leftImageLink = new LinkedResource(imageSource, "image/gif")
                                        {
                                            ContentId = fbody.Substring(0, comma),
                                            TransferEncoding = System.Net.Mime.TransferEncoding.Base64
                                        };
                                        break;
                                    case ".png":
                                        leftImageLink = new LinkedResource(imageSource, "image/png")
                                        {
                                            ContentId = fbody.Substring(0, comma),
                                            TransferEncoding = System.Net.Mime.TransferEncoding.Base64
                                        };
                                        break;
                                }
                                htmlView.LinkedResources.Add(leftImageLink);
                            }
                        }
                    }
                }
            }
            while (fbody.Contains("src='cid:"));
            msg.AlternateViews.Add(htmlView);

此处imagesource无法访问其他Web应用程序文件夹图像。这里出了什么问题..