[HttpGet]
[Route("api/teststring")]
public HttpResponseMessage TestString()
{
	var response = new HttpResponseMessage();
	response.Content = new StringContent("test", System.Text.Encoding.UTF8, "text/plain");
	return response;
}

{"Version":{"_Major":1,"_Minor":1,"_Build":-1,"_Revision":-1},"Content":{"Headers":[{"Key":"Content-Type","Value":["text/plain; charset=utf-8"]}]},"StatusCode":200,"ReasonPhrase":"OK","Headers":[],"RequestMessage":null,"IsSuccessStatusCode":true}