如何为便携HttpClient实现进度报告

Answer 1

我编写了以下代码来实现进度报告。代码支持我想要的所有平台；但是，您需要引用以下NuGet包：

• Microsoft.net.http
• Microsoft.bcl.Async

代码如下：

public async Task DownloadFileAsync(string url, IProgress<double> progress, CancellationToken token)
{
    var response = await client.GetAsync(url, HttpCompletionOption.ResponseHeadersRead, token);

    if (!response.IsSuccessStatusCode)
    {
        throw new Exception(string.Format("The request returned with HTTP status code {0}", response.StatusCode));
    }

    var total = response.Content.Headers.ContentLength.HasValue ? response.Content.Headers.ContentLength.Value : -1L;
    var canReportProgress = total != -1 && progress != null;

    using (var stream = await response.Content.ReadAsStreamAsync())
    {
        var totalRead = 0L;
        var buffer = new byte[4096];
        var isMoreToRead = true;

        do
        {
            token.ThrowIfCancellationRequested();

            var read = await stream.ReadAsync(buffer, 0, buffer.Length, token);

            if (read == 0)
            {
                isMoreToRead = false;
            }
            else
            {
                var data = new byte[read];
                buffer.ToList().CopyTo(0, data, 0, read);

                // TODO: put here the code to write the file to disk

                totalRead += read;

                if (canReportProgress)
                {
                    progress.Report((totalRead * 1d) / (total * 1d) * 100);
                }
            }
        } while (isMoreToRead);
    }
}

var progress = new Microsoft.Progress<double>();
progress.ProgressChanged += (sender, value) => System.Console.Write("\r%{0:N0}", value);

var cancellationToken = new CancellationTokenSource();

await DownloadFileAsync("http://www.dotpdn.com/files/Paint.NET.3.5.11.Install.zip", progress, cancellationToken.Token);