.net core has new behavior for returning string, different from .net web api

[zijianhuang]

as described at aspnet/Mvc#4945

And the content type becomes text/plain, rather than json

[zijianhuang]

It will be up to the application programmers to either alter the Accept headers of HttpClient, or alter the behavior of .NET Core Web API. For example:

httpClient = new System.Net.Http.HttpClient();
httpClient.DefaultRequestHeaders
	  .Accept
	  .Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));

[zijianhuang]

StringAsString option