New Post: JSON String Conversion Problems.

I can't reproduce this. I get the expected { "Hello" : "World" } when I use the WP8 library to create a JSON payload. BTW, you don't have to serialize to a string yourself, you can just use the request() overload that takes a JSON value:

json::value v; 
v[L"Hello"] = json::value::string(U("World")); 

client.request(methods::POST, L"", v).then[](http_response response) { 
    // more code here 
} 

If you try it with a Windows desktop or app store app, what happens? Can you use fiddler with the emulator to see what actually is sent on the wire?

Are you using some locale other than Western European? We haven't tested on a lot of non-WE locales (Japan is the only East Asian we've tried things on, I believe, for example).