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When I'm using DeleteAsync function in HttpClient (System.Net.Http) and retrieve the content with Content.ReadAsStringAsync() I always get null returned.

I've tried the same with GET, POST and PUT - and they always return some result.

Here is my code:

HttpClient _client = new HttpClient();
_client.BaseAddress = new Uri("http://httpbin.org/");
_client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
HttpResponseMessage response = _client.DeleteAsync("/delete").Result;
string res = await response.Content.ReadAsStringAsync();
return await JsonConvert.DeserializeObjectAsync<T>(res);

I always get null returned.

However, all of this works:

GET:

HttpResponseMessage response = _client.GetAsync("/get").Result;
string res = await response.Content.ReadAsStringAsync();
return await JsonConvert.DeserializeObjectAsync<T>(res);

POST:

HttpResponseMessage response = _client.PostAsync("/post", new StringContent(JsonConvert.SerializeObject(obj), Encoding.UTF8, "application/json")).Result;
string res = await response.Content.ReadAsStringAsync();
return await JsonConvert.DeserializeObjectAsync<T>(res);

PUT:

HttpResponseMessage response = _client.PutAsync("/put", new StringContent(JsonConvert.SerializeObject(obj), Encoding.UTF8, "application/json")).Result;
string res = await response.Content.ReadAsStringAsync();
return await JsonConvert.DeserializeObjectAsync<T>(res);

But DeleteAsync() and ReadAsStringAsync() always return me null.

According to RFC you have to return body when returning status code 200 OK.

share|improve this question
Have you tried to use Fiddler to see what's going on on the wire? – Paulo Morgado Jul 14 at 19:43
1  
Shouldn't make a difference on the result, but any reason why you block (call .Result) on DeleteAsync instead of awaiting it? – cremor Jul 15 at 5:15
@cremor Rookie mistake. – Gaui Jul 15 at 13:31

1 Answer

up vote 0 down vote

Your code never checks the message response for the StatusCode. Unlike WebClient, HttpClient does NOT throw when the StatusCode is not in the 2xx range.

I bet that if you check the HttpResponseMessage.StatusCode/HttpResonseMessage.ReasonPhrase values you will find that the server returned a code other than 200.

For example:

HttpClient _client = new HttpClient();
_client.BaseAddress = new Uri("http://httpbin.org/");
...
var response = await _client.DeleteAsync("/delete");
if (response.IsSuccessStatusCode)
{
    var result=await response.Content.ReadAsStringAsync();
    ....
}

You can also call the EnsureSuccessStatusCode method to throw an exception if the response status is not a success code:

HttpClient _client = new HttpClient();
_client.BaseAddress = new Uri("http://httpbin.org/");
...
var response = await _client.DeleteAsync("/delete");
response.EnsureSuccessStatusCode();
var result=await response.Content.ReadAsStringAsync();

EDIT

By the way, running the following as is on .NET 4.5, returns a body:

        var  _client = new HttpClient();
        _client.BaseAddress = new Uri("http://httpbin.org/");
        var response = await _client.DeleteAsync("/delete");
        if (response.IsSuccessStatusCode)
        {
            var result = await response.Content.ReadAsStringAsync();
            Console.WriteLine(result);

        }

Adding the Accept header doesn't make any difference

share|improve this answer
Changed my code to use response.EnsureSuccessStatusCode(); - but that didn't change anything. The server respondes with 200 OK. But I always get null. pastebin.com/dKb8BfBD – Gaui Jul 15 at 13:35
Why do you thing this is wrong? The server may not have sent a body. You should check the server's API to see whether it returns anything on a DELETE. Besides, not all REST APIs respect the RFCs – Panagiotis Kanavos Jul 15 at 13:43
I'm guessing ASP.NET Web API doesn't respect it. Because the method I'm using to deliver the data is exactly the same as POST and PUT. Weird. – Gaui Jul 15 at 15:13
ASP.NET Web API returns what you tell it to return. If you don't return anything for the DELETE verb, there is nothing to return. In other words, check your code – Panagiotis Kanavos Jul 15 at 17:34

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