public static class HttpClientExtensions
{
public static async Task DownloadAsync(this HttpClient client, string requestUri, Stream destination, IProgress<float>? progress = null, CancellationToken cancellationToken = default)
{
// Get the http headers first to examine the content length
var response = await client.GetAsync(requestUri, HttpCompletionOption.ResponseHeadersRead);
var contentLength = response.Content.Headers.ContentLength;
await using var download = await response.Content.ReadAsStreamAsync();

// Ignore progress reporting when no progress reporter was
// passed or when the content length is unknown
if (progress == null || !contentLength.HasValue)
{
await download.CopyToAsync(destination);
return;
}

// Convert absolute progress (bytes downloaded) into relative progress (0% - 100%)
var relativeProgress = new Progress<long>(totalBytes => progress.Report((float)totalBytes / contentLength.Value));
// Use extension method to report progress while downloading
await download.CopyToAsync(destination, 81920, relativeProgress, cancellationToken);
progress.Report(1);
}
}
}