即使使用ConfigureAwait（false），HttpClient的PostAsync方法也会阻塞

Question

I've spent many hours trying to figure this one out, but unfortunately to no avail. I'd be grateful for any help.

The problem is that the PostAsync call blocks event though I use await and ConfigureAwait(false) . The below handler is called on the UI thread:

private async void OnApplicationLaunching(object sender, LaunchingEventArgs e)
{
    using (var httpClient = new HttpClient())
    {
        var content = new List<KeyValuePair<string, string>>();

        var urlEncodedContent = new FormUrlEncodedContent(content);

        await httpClient.PostAsync("url address", urlEncodedContent).ConfigureAwait(false);
    }
}

Edit 1

• I use WindowsPhone 8.0 silverlight
• In my opinion it is a deadlock. The execution is blocked until the exception appears with "task got canceled" message
• I am not interested in "fire and forget". I need to be sure that the data is sent before allowing further execution.

Edit 2

Here's another code sample which does not differ alot from previous one, but beter resembles the code samples from Stephen's blog

Section "Preventing the Deadlock" in http://blog.stephencleary.com/2012/07/dont-block-on-async-code.html

Section "Avoiding Context" in http://blog.stephencleary.com/2012/02/async-and-await.html

private async void OnApplicationLaunching(object sender, LaunchingEventArgs e)
{
    await this.SendSth();

    // here I want to know for sure that data has already been sent
}

private async Task SendSth()
{
    using (var httpClient = new HttpClient())
    {
        var content = new List<KeyValuePair<string, string>>();

        var urlEncodedContent = new FormUrlEncodedContent(content);

        await httpClient.PostAsync("some url", urlEncodedContent).ConfigureAwait(false);
    }
}

By the way, thanks Stephen for your great articles. They help alot.

Answer 1

From my understanding of asynchronous programming in C#, ConfigureAwait should be called in library.

See this article from Stephen Cleary. Check this also.