Use with SP-API

[pedrogabe]

Hi!
Has anybody use this to make requests to the Amazon Selling Partner API?
Everything I try gives me the same response: "The request signature we calculated does not match the signature you provided. Check your AWS Secret Access Key and signing method. Consult the service documentation for details"
I admit I don't have much experience with the SP-API. Any suggestions are welcome

[FantasticFiasco]

I don't have any experience myself using this the SP-API. Let's leave this discussion open and see if anyone has any experience of it.

[pedrogabe]

I have reached a solution for this problem by myself.
According to Amazon SP-API documentation a "User-Agent" header is required, and its value should comply with the following format:
AppId/AppVersionId (Language=LanguageNameAndOptionallyVersion)
I tried to add this header as a default request header of my HttpClient with a code line similar to this:
client.DefaultRequestHeaders.Add(Amazon.Util.HeaderKeys.UserAgentHeader, "App/0.0 (Language=Csharp)");

Yet, this Add method converted my string into two different values splitting it by the space character. Hence, the CanonicalRequest class included a comma in the canonical string that Amazon was not expecting.
I temporarily solved it by modifying the CanonicalRequest.HeaderValueSeparator value, though I understand this is not correct since the separator for the values should remain a comma as it is specified in the AWS documentation

If anybody knows a way of including the header value including space characters without it being split, I'll appreciate the tip. In conclussion, I see no real bugs in the code and it has turned out to be very useful.

[FantasticFiasco]

Thanks for analyzing the issue and finding the solution!

Without knowing anything about the SP-API, is there a way to uniquely identify requests to that API, like the service name?

[pedrogabe]

The service name is "execute-api", which doesn't sound very unique. I understand the possible host Headers are "sellingpartnerapi-na.amazon.com", "sellingpartnerapi-eu.amazon.com" and "sellingpartnerapi-fe.amazon.com", according to the endpoints listed in the documentation.
I'll let you know if I find anything more reliable.