HttpResponseMessage.Content.ReadAsStreamAsync() vs HttpResponseMessage.Content.ReadAsStringAsync()

Question

var request = new HttpRequestMessage(HttpMethod.Get, $"api/Items");
request.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

using (var response = await _httpClient.SendAsync(request))
{
   response.EnsureSuccessStatusCode();
   var stream = await response.Content.ReadAsStreamAsync();        

     using (var streamReader = new StreamReader(stream))
     {
       using (var jsonTextReader = new JsonTextReader(streamReader))
       {
         var jsonSerializer = new JsonSerializer();
         var data =  jsonSerializer.Deserialize<Item>(jsonTextReader);
       }
     }
}

...

var request = new HttpRequestMessage(HttpMethod.Get, "api/Items");
request.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
var response = await _httpClient.SendAsync(request);

response.EnsureSuccessStatusCode();

var content = await response.Content.ReadAsStringAsync();
var data = JsonConvert.DeserializeObject<List<Item>>(content);

I've run this two examples and I'm curious what is the difference between them that always getting same result, ReadAsStreamAsync is much faster then ReadAsStringAsync.

Answer 1

Under the hood, HttpClient stores content in MemoryStream. So, basically calling ReadAsStreamAsync just returns a reference to the stream. In the case of calling ReadAsStringAsync, ToArray method is called on memory stream so an additional copy of data is created.

Answer 2

You can check description for ReadAsStreamAsync and for ReadAsStringAsync

In few words - you can send to request content not only string. And ReadAsStreamAsync is only way for you here. If your response content is string - you can use both. But Stream is faster in Any Time.

This gives good explanation about memory allocation and perfomanse in these cases.