How can I use System.Net.HttpWebRequest with async/await?

Question

I've been trying to write a simple HTTP client as a Portable Class Library with minimum dependencies, which made me think that I should use System.Net.HttpWebRequest.

I've looked at the documentation, but it shows only GetResponse/GetResponseStream methods, which I don't have in my implementation. I only have BeginGetResponse, BeginGetResponseStream, etc. I've tried using Task.Factory.FromAsync to convert this to a Task, but that only returns a Task, not a Task<HttpWebResponse>.

Is the correct approach here to use a cast, such as the following?

var response = (Task<HttpWebResponse>)Task.Factory.FromAsync(request.BeginGetResponse, request.EndGetResponse);

Or am I missing something?

edit: I don't want to introduce dependencies on additional NuGet packages, since all I need to do is a single HTTP request in one place in a tiny library.

You should use GetResponseAsync. Not sure if that's available in a PCL though. The System.Net.HttpClient NuGet package is probably a better choice than using HttpWebRequest. — Cory Nelson
– Cory Nelson, Commented Aug 26, 2014 at 14:54
I would strongly suggest using System.Net.Http.HttpClient (nuget.org/packages/Microsoft.Net.Http) — tpeczek
– tpeczek, Commented Aug 26, 2014 at 14:54
You were looking in the wrong place. The full documentation is at WebRequest class. — John Saunders
– John Saunders, Commented Aug 26, 2014 at 14:59
But that means I need to add dependencies to my library. All I'm really doing is just a single HTTP request, it feels like an overkill to add a nuget package just for that. — Jakub Arnold
– Jakub Arnold, Commented Aug 26, 2014 at 15:11
@JakubArnold: But this NuGet package is focused on doing exactly what you need. Would you object to adding a reference to Microsoft.Net.Http if it was part of the base class library and not a download? Like it or not Microsoft is delivering more and more class libraries using NuGet. — Martin Liversage
– Martin Liversage, Commented Aug 26, 2014 at 15:29

StriplingWarrior · Accepted Answer · 2014-08-26 15:38:44Z

1

If you use a generic Task<>.Factory you get a little more type-safety:

var request = WebRequest.CreateHttp("https://www.google.com");
object state = null; // or whatever state you want.
var task = Task<WebResponse>.Factory.FromAsync(
    request.BeginGetResponse,
    request.EndGetResponse, 
    state);

However, as with when you're not doing async calls, if you want an HttpWebResponse rather than just a WebResponse, you'll need to do an additional cast. And be sure to close/dispose your response:

using (var response = (HttpWebResponse) (await task))
{
    // use response
}

answered Aug 26, 2014 at 15:38

StriplingWarrior

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