Amazon Feed API-文件'；s标题行丢失或无效

我正在尝试提交一个充满产品的平面文件（以制表符分隔）。如果我通过upload Products&库存页面上传正确。然而，如果我尝试使用API，我会得到一个错误：

The file's header row is missing or invalid. The header row is for Amazon use only and must not be modified or deleted. To correct this error, download the template again from seller Help and use that new copy, or insert the correct header row directly above the column headings in your existing file.

我使用的代码是示例代码，Feeds API部分客户端库-C#。

SubmitFeedRequest request = new SubmitFeedRequest();
request.Merchant = merchantId;
request.MarketplaceIdList = new IdList();
request.MarketplaceIdList.Id = new List<string>(new string[] { marketplaceId });

request.FeedContent = File.Open(@"C:'Amazon_Upload_20141104_10.txt", FileMode.Open, FileAccess.Read);

request.ContentMD5 = MarketplaceWebServiceClient.CalculateContentMD5(request.FeedContent);
request.FeedContent.Position = 0;
request.FeedType = "_POST_FLAT_FILE_LISTINGS_DATA_";
SubmitFeedSample.InvokeSubmitFeed(service, request);

为什么这个文件可以通过web界面工作而不能通过API？