amazon mws - MWS fba api bad request c# -

hi testing marketplacewebservice.samples.but responses alway bad request. invaild request. can take look. thanks.

submitfeedrequest request = new submitfeedrequest();             request.merchant = merchantid;             request.mwsauthtoken = "<your mws auth token>"; // optional             request.marketplaceidlist = new idlist();             request.marketplaceidlist.id = new list<string>(new string[] { marketplaceid });                request.feedcontent = file.open("feed.xml", filemode.open, fileaccess.read);               request.contentmd5 = marketplacewebserviceclient.calculatecontentmd5(request.feedcontent);             request.feedcontent.position = 0;              request.feedtype = "_post_product_data_";              submitfeedsample.invokesubmitfeed(service, request); 

feed.xml 1.01 machantid product false 1 update testsku upc 123456789