Async call with HttpClient in PCL

Question

I have a PCl in which I want to make a async call usingg HttpClient. I coded like this

 public static async Task<string> GetRequest(string url)
    {            
        var httpClient = new HttpClient() { MaxResponseContentBufferSize = int.MaxValue };
        HttpResponseMessage response = await httpClient.GetAsync(url);
        return response.Content.ReadAsStringAsync().Result;
    }

But await is showing error "cannot await System.net.http.httpresponsemessage" like message.

If I use code like this than everything goes well but not in async way

public static string GetRequest(string url)
    {
        var httpClient = new HttpClient() { MaxResponseContentBufferSize = int.MaxValue };
        HttpResponseMessage response = httpClient.GetAsync(url).Result;
        return response.Content.ReadAsStringAsync().Result;
    }

I just want that this method executes in async way.

This is the screen shot:

enter image description here

What do you mean by "error": a compilation error or a runtime exception? What's the exact error message? — Solal Pirelli, Mar 26 '14 at 10:50
Please show the *exact* error message. I'm sure it isn't just "cannot await". — Jon Skeet, Mar 26 '14 at 10:50

Stephen Cleary · Accepted Answer · 2014-03-26T23:49:28.963

6

Follow the TAP guidelines, don't forget to call EnsureSuccessStatusCode, dispose your resources, and replace all Results with awaits:

public static async Task<string> GetRequestAsync(string url)
{            
  using (var httpClient = new HttpClient() { MaxResponseContentBufferSize = int.MaxValue })
  {
    HttpResponseMessage response = await httpClient.GetAsync(url);
    response.EnsureSuccessStatusCode();
    return await response.Content.ReadAsStringAsync();
  }
}

If your code doesn't need to do anything else, HttpClient has a GetStringAsync method that does this for you:

public static async Task<string> GetRequestAsync(string url)
{            
  using (var httpClient = new HttpClient() { MaxResponseContentBufferSize = int.MaxValue })
    return await httpClient.GetStringAsync(url);
}

If you share your HttpClient instances, this can simplify to:

private static readonly HttpClient httpClient =
    new HttpClient() { MaxResponseContentBufferSize = int.MaxValue };
public static Task<string> GetRequestAsync(string url)
{            
  return httpClient.GetStringAsync(url);
}

edited Mar 26 '14 at 23:49

answered Mar 26 '14 at 11:48

Stephen Cleary

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@ta.speot.is: Answered [here](http://stackoverflow.com/questions/15705092/do-httpclient-and-httpclienthandler-have-to-be-disposed). – Stephen Cleary Mar 26 '14 at 12:21
@ta.speot.is When used this way, then yes it should be disposed. However, creating a new instance for each request is not the optimum way of using HttpClient. – Darrel Miller Mar 26 '14 at 12:32
Updated to properly handle resources. – Stephen Cleary Mar 26 '14 at 12:47
@StephenCleary I am getting same error on using your code, Please check the updated part of question. – mayank.karki Mar 29 '14 at 18:52
@mayank.karki: Install the `Microsoft.Bcl.Async` NuGet package. – Stephen Cleary Mar 29 '14 at 19:37

score 1 · Answer 2 · answered Mar 26 '14 at 12:33

1

If you are using a PCL platform that supports .net4 then I suspect you need to install the Microsoft.bcl.Async nuget.

answered Mar 26 '14 at 12:33

Darrel Miller

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Async call with HttpClient in PCL

2 Answers2

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