ASP.NET:System.UnauthorizedAccessException-拒绝访问路径

我有一个ASP.NET Web应用程序,它执行以下操作:

1. 读取Excel文件。
2. Excel文件中会有一个指向Internet上某个位置的图像URL。
3. 程序读取每个图像URL并将其存储到Web服务器的临时文件夹中。
4. 然后应用程序调整图像的大小(更改宽度和高度)。

5. 最后,应用程序会将该图像保存到另一个文件夹中。

   我收到以下例外情况:

System.net.WebException:异常 在WebClient请求期间发生。 --->系统。未授权访问异常: 访问路径 '\abcserver\target03\3111\35644\www.testing.com\web\content\images\tempstorage\tempimage.jpg' 被拒绝。在 System.IO.\u错误.WinIOError(Int32 错误代码,字符串maybefullpath)at system.io.filestream.init(字符串路径, 文件模式,文件访问访问, Int32权限,布尔用户权限, 文件共享共享,Int32缓冲区大小, 文件选项选项, 安全属性secattrs,string msgpath,boolean bfromproxy)位于 system.io.filestream..ctor(字符串 路径,文件模式,文件访问 访问) System.NET.WebClient.DownloadFile(URI 地址,字符串文件名)---结束 内部异常堆栈跟踪---
在processimage.getfilefromurl(字符串 imagefileurl,字符串newfilename)
在 uploadExcelData.uploadExcelData(字符串 文件名)

 foreach (DataRow dr in dt.Rows) // Reading each excel row
            {

                if (dr[0].ToString() != "")
                {
                    id= "";
                    path = "";
                    manuId = "";


                    id= dr[0].ToString();
                    path = dr[1].ToString();
                    fileNameOnly = iProImg.GetFileNameOnly(path);
                    objDb.openConnection();
                    strSqlGroupInfo = "select ManufacturerID from  manufacturers where id='" + id+ "'";

                    dTblManu = objDb.BuildDT(strSqlGroupInfo); // To Fill data to Datatable
                    objDb.closeConnection();
                    if (dTblManu.Rows.Count > 0)
                    {
                        manuId = dTblManu.Rows[0][0].ToString();
                    }

                    if (manuId != "")
                    {
                        tempUploadPath = "images/TempStorage/";
                        tempUploadPath = Server.MapPath(tempUploadPath);
                        if (!Directory.Exists(tempUploadPath))
                        {
                            Directory.CreateDirectory(tempUploadPath);
                        }
                        tempFilePath = tempUploadPath + "\\tempImage.jpg";
                        tempFilePath = tempFilePath.Replace("/", "\\");

                        previewPath = Server.MapPath("images/previews/" + manuId);
                        thumbNailPath = Server.MapPath("images/thumbnails/" + manuId);

                        if (!Directory.Exists(previewPath))
                        {
                            Directory.CreateDirectory(previewPath);
                        }
                        if (!Directory.Exists(thumbNailPath))
                        {
                            Directory.CreateDirectory(thumbNailPath);
                        }
                        fileNameOnly = "\\preview" + id+ ".jpg";
                        fileNameOnly = fileNameOnly.Replace("/", "\\");
                        previewPath = previewPath + fileNameOnly;
                        tempPartialPathP = "images\\previews\\" + manuId + fileNameOnly;

                        fileNameOnly = "\\thumbnail" + id+ ".jpg";
                        thumbNailPath = thumbNailPath + fileNameOnly;
                        tempPartialPathT = "images\\thumbnails\\" + manuId + fileNameOnly;


                        try
                        {

                            iProImg.GetFileFromUrl(path, tempFilePath);
                            rowCounter++;
                            iProImg.ReSizeImage(tempFilePath, previewPath, previewSize);
                            iProImg.ReSizeImage(previewPath, thumbNailPath, thumbNailSize);

                        }
                        catch (Exception ec)
                        {

                            errorRowCount++;
                            iLog.LogErrorToFile("uploadExcel", ec.ToString(), "path : " + path + ",tempFilePath :" + tempFilePath);


                        }
                        finally
                        {
                            if(File.Exists(tempFilePath))
                            {
                            File.Delete(tempFilePath);
                            }
                        }
                    } // If manuid!=""
                }  //if (dr[0].ToString() != "")

有人对如何修复这个异常有什么建议吗?