在我的 Windows 应用商店应用程序 (c#) 中,我需要将 MultipartFormDataContent
(一些字符串内容和一些文件)上传到服务器并在响应时获得一个巨大的文件。问题 - 我不能为此使用 BackgroundDownloaders
。我只能为此使用一个请求。
我使用 HttpClient.PostAsync
方法:
using (var client = new HttpClient(httpClientHandler))
{
using (var content = new MultipartFormDataContent())
{
content.Add(...); // prepare all strings and files content
try
{
using (var response = await client.PostAsync(url, content))
{
if (response.StatusCode == HttpStatusCode.OK)
{
var inputBytes = await response.Content.ReadAsByteArrayAsync();
// some operations with inputBytes
}
......
}
}
}
}
我的问题是:如何计算此操作的进度?
注意:我的目标是 Windows 8。而且我不能使用 Windows.Web.Http.HttpClient
(支持的最低客户端 Windows 8.1)。只有 System.Net.Http.HttpClient
最佳答案
我遇到了同样的问题。我通过实现自定义 HttpContent
修复了它。我使用这个对象来跟踪上传进度的百分比,你可以添加一个事件并监听它。您应该自定义 SerializeToStreamAsync
方法。
internal class ProgressableStreamContent : HttpContent
{
private const int defaultBufferSize = 4096;
private Stream content;
private int bufferSize;
private bool contentConsumed;
private Download downloader;
public ProgressableStreamContent(Stream content, Download downloader) : this(content, defaultBufferSize, downloader) {}
public ProgressableStreamContent(Stream content, int bufferSize, Download downloader)
{
if(content == null)
{
throw new ArgumentNullException("content");
}
if(bufferSize <= 0)
{
throw new ArgumentOutOfRangeException("bufferSize");
}
this.content = content;
this.bufferSize = bufferSize;
this.downloader = downloader;
}
protected override Task SerializeToStreamAsync(Stream stream, TransportContext context)
{
Contract.Assert(stream != null);
PrepareContent();
return Task.Run(() =>
{
var buffer = new Byte[this.bufferSize];
var size = content.Length;
var uploaded = 0;
downloader.ChangeState(DownloadState.PendingUpload);
using(content) while(true)
{
var length = content.Read(buffer, 0, buffer.Length);
if(length <= 0) break;
downloader.Uploaded = uploaded += length;
stream.Write(buffer, 0, length);
downloader.ChangeState(DownloadState.Uploading);
}
downloader.ChangeState(DownloadState.PendingResponse);
});
}
protected override bool TryComputeLength(out long length)
{
length = content.Length;
return true;
}
protected override void Dispose(bool disposing)
{
if(disposing)
{
content.Dispose();
}
base.Dispose(disposing);
}
private void PrepareContent()
{
if(contentConsumed)
{
// If the content needs to be written to a target stream a 2nd time, then the stream must support
// seeking (e.g. a FileStream), otherwise the stream can't be copied a second time to a target
// stream (e.g. a NetworkStream).
if(content.CanSeek)
{
content.Position = 0;
}
else
{
throw new InvalidOperationException("SR.net_http_content_stream_already_read");
}
}
contentConsumed = true;
}
}
仅供引用:
public interface IDownload
{
event EventHandler<DownloadStateEventArgs> StateChanged;
event EventHandler<DownloadStateEventArgs> Completed;
DownloadState State { get; }
Guid Id { get; }
string Uri { get; }
long Filesize { get; }
long Downloaded { get; }
Task DownloadAsync();
}
关于c# - 如何使用 HttpClient PostAsync 计算进度?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/22528839/