Post_Product_Data as JSON

[Lemodo20]

Hi,

because i've got an email from Amazon, that txt/XML Files are soon not supported any more, i changed my structure to JSON.
I created already an valid JSON to submit it with the Function

feedresultTXT = amazonConnection.Feed.SubmitFeed(File, Reporttype, marketplaceIds, Nothing, ContentType.JSON)

i use the same function, i've used before for XML file. Only the content inside the file and the file extension is differnt. Also i defined the content type as ContentType.JSON.

but i always get from Amazon back, that i submit an invalid XML-File.
XML Parsing Fatal Error at Line 1, Column 1: Content is not allowed in prolog. Content is not allowed in prolog.

Is this maybe an Bug in the API?