Content.ReadAsAsync 总是给 null

Question

I am facing issue in reading consents using Content.ReadAsAsync . Have a look at my code.

private HttpResponseMessage _responseMessage;
_responseMessage = UnitTestHelper.Get(string.Format("api/StudentController/Get/?StartDate={0}&EndDate={1}", DateTime.Now, DateTime.Now));
Assert.IsTrue(_responseMessage.IsSuccessStatusCode);
Assert.IsTrue(_responseMessage.Content.ReadAsAsync<List<StudentModel>>().Result.Count > 0);
var auditData = _responseMessage.Content.ReadAsStringAsync().Result;
_responseMessage.Content.ReadAsAsync<List<StudentModel>>().Result;

Outcome of above code:

• It successfully make post call, gets the result back.

• Result.Count shows 1.

• ReadAsStringAsync shows data in the following format.

   [{\\"User\\":\\"Test\\",\\"Location\\":\\"MyCountry\\",\\"Class\\":\\"Grade1\\",\\"Time\\":\\"2016-07-06T07:26:11.183\\",\\"SchoolName\\":\\"ABC School System\\"}]

• Last line gives null. I am expecting a list here.

My Problem.

The following line of code always shows null. Whereas I am expecting to have list.

_responseMessage.Content.ReadAsAsync<List<StudentModel>>().Result;

Why? What is wrong here?

Answer 1

The problem is that you're calling _responseMessage.Content.ReadAsAsync<List<StudentModel>>() twice. You should store the result in some variable and then work with it

var result = _responseMessage.Content.ReadAsAsync<List<StudentModel>>().Result;
Assert.IsTrue(result.Count > 0);
//do whatever needed with result

Also you'd better utilize async/await instead of calling .Result

---

To be more specific ReadAsAsync<T> uses internaly HttpContent.ReadAsStreamAsync which caches memory stream and once it is read Position stays at the end of the stream.

Answer 2

You have to update NewtonSoft.json.dll to the latest. This should work.