ConfigureAwaitWindow.xaml.cs

using Microsoft.Extensions.DependencyInjection;

using System.IO;
using System.Net.Http;
using System.Windows;

namespace AsyncAwait;

/// <summary>
/// Interaction logic for ConfigureAwaitWindow.xaml
/// </summary>
public partial class ConfigureAwaitWindow : Window
{
    private readonly IHttpClientFactory clientFactory;

    public ConfigureAwaitWindow()
    {
        InitializeComponent();

        var services = new ServiceCollection();
        services.AddHttpClient();
        this.clientFactory = services.BuildServiceProvider().GetRequiredService<IHttpClientFactory>();
    }

    private async void OnFetchButtonClick(object sender, RoutedEventArgs e)
    {
        using (HttpClient w = this.clientFactory.CreateClient())
        using (Stream f = File.Create(fileTextBox.Text))
        {
            Task<Stream> getStreamTask = w.GetStreamAsync(urlTextBox.Text);
            Stream getStream = await getStreamTask.ConfigureAwait(false);

            Task copyTask = getStream.CopyToAsync(f);
            await copyTask.ConfigureAwait(ConfigureAwaitOptions.None);
        }
    }
}