获取文件数据异常！System.IO.PathTooLongException: 指定的路径或文件名太长，或者两者都太长。完全限定文件名必须少于 260 个字符，并且目录名必须少于 248 个字符。
   在 System.IO.Path.LegacyNormalizePath(String path, Boolean fullCheck, Int32 maxPathLength, Boolean expandShortPaths)
   在 System.IO.Path.GetFullPathInternal(String path)
   在 System.Security.Util.StringExpressionSet.CanonicalizePath(String path, Boolean needFullPath)
   在 System.Security.Util.StringExpressionSet.CreateListFromExpressions(String[] str, Boolean needFullPath)
   在 System.Security.Permissions.FileIOPermission.AddPathList(FileIOPermissionAccess access, AccessControlActions control, String[] pathListOrig, Boolean checkForDuplicates, Boolean needFullPath, Boolean copyPathList)
   在 System.Security.Permissions.FileIOPermission.AddPathList(FileIOPermissionAccess access, String[] pathListOrig, Boolean checkForDuplicates, Boolean needFullPath, Boolean copyPathList)
   在 System.Security.Permissions.FileIOPermission..ctor(FileIOPermissionAccess access, String path)
   在 System.Web.InternalSecurityPermissions.PathDiscovery(String path)
   在 System.Web.HttpRequest.MapPath(VirtualPath virtualPath, VirtualPath baseVirtualDir, Boolean allowCrossAppMapping)
   在 System.Web.HttpServerUtility.MapPath(String path)
   在 linker_allfile.ProcessRequest(HttpContext c)