public async Task Post()
{
var response = await _client.PostAsync("/sample/Products(1L)/Categories/$ref", Helpers.JSON(new Dictionary <string, object> {
["@odata.id"] = "http://localhost/sample/Categories(2)"
}));
Assert.Equal(HttpStatusCode.OK, response.StatusCode);
response = await _client.GetAsync("/sample/Products(1L)/Categories(2)");
Assert.Equal(HttpStatusCode.OK, response.StatusCode);
}