CODEWITHSUNDEEP
c#httpclient
Nathan
Nathan

Reputation: 7709

cancel a c# httpClient GetStreamAsync call

I need to add the possibility of canceling an http request in an old c# project.

The project uses HttpClient::GetStreamAsync which does not seem to support Cancellation tokens.

Can a GetStreamAsync call be canceled? What other possibilities do I have?

Upvotes: 9

Views: 2862

Answers (3)

kevin628
kevin628

Reputation: 3526

2022 Update: I have left the link to the MSDN article because at the moment I write this the link still works. However, the link is older and may eventually cease to work, and I noticed the code formatting I saw back in 2017 is no longer there today. Additionally, based on comments below my answer, I have lightly edited the content of my answer to remove an unhelpful sentence as well as a pointlessly italicized word.

Original Answer: I spotted an alternative solution from a MSDN blog post written in 2012. It might be of some help to you. The author is using GetStringAsync but the principle also applies to GetStreamAsync. Article: Await HttpClient.GetStringAsync() and cancellation.

In the MSDN article the author is using GetAsync(...) which can take a cancellation parameter. A simple solution for Nathan's issue could be something like this...

CancellationTokenSource cancellationSource = new CancellationTokenSource();
CancellationToken cancellationToken = cancellationSource.Token;

Uri uri = new Uri("some valid web address"); 
HttpClient client = new HttpClient();
await client.GetAsync(uri, cancellationToken);

// In another thread, you can request a cancellation.
cancellationSource.Cancel();

Note that the cancellation is made on the CancellationTokenSource object, not the CancellationToken object.

Upvotes: 7

Red Riding Hood
Red Riding Hood

Reputation: 2474

Same as Johns answer, just as an extension method:

 internal static class HttpClientExtensions
    {
        public async static Task<Stream> GetStreamAsync(this HttpClient httpClient, string url, CancellationToken ct)
        {
            var response = await httpClient.GetAsync(new Uri(url), ct);
            return await response.Content.ReadAsStreamAsync();
        }
    }

Upvotes: 0

John Henckel
John Henckel

Reputation: 11417

Here is a simple example.

public async Task<Stream> GetWebData(string url, CancellationToken? c = null)
{
    using (var httpClient = new HttpClient())
    {
        var t = httpClient.GetAsync(new Uri(url), c ?? CancellationToken.None);
        var r = await t;
        return await r.Content.ReadAsStreamAsync();
    }
}

Upvotes: 6

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