使用 HttpClient,如何将 XDocument 直接保存到请求流中?
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【中文标题】使用 HttpClient,如何将 XDocument 直接保存到请求流中?【英文标题】:using HttpClient, how can I save a XDocument directly to the request stream? 【发布时间】:2012-02-11 18:28:34 【问题描述】:使用 HttpWebRequest,我可以调用 XDocument.Save() 将直接写入请求流:
XDocument doc = ...;
var request = (HttpWebRequest)WebCreate.Create(uri);
request.method = "POST";
Stream requestStream = request.GetRequestStream();
doc.Save(requestStream);
HttpClient
可以做同样的事情吗?直接的方法是
XDocument doc = ...;
Stream stream = new MemoryStream();
doc.Save(stream);
var content = new System.Net.Http.StreamContent(stream);
var client = new HttpClient();
client.Post(uri, content);
但这会在MemoryStream
中创建XDocument
的另一个副本。
【问题讨论】:
【参考方案1】:XDocument.Save()
需要一个可以写入的Stream
。 StreamContent
需要一个可以读取的流。因此,您可以使用两个Stream
s,其中一个充当另一个的转发器。我认为框架中不存在这种类型,但您可以自己编写一个:
class ForwardingStream
private readonly ReaderStream m_reader;
private readonly WriterStream m_writer;
public ForwardingStream()
// bounded, so that writing too much data blocks
var buffers = new BlockingCollection<byte[]>(10);
m_reader = new ReaderStream(buffers);
m_writer = new WriterStream(buffers);
private class ReaderStream : Stream
private readonly BlockingCollection<byte[]> m_buffers;
private byte[] m_currentBuffer;
private int m_readFromCurrent;
public ReaderStream(BlockingCollection<byte[]> buffers)
m_buffers = buffers;
public override void Flush()
public override long Seek(long offset, SeekOrigin origin)
throw new NotSupportedException();
public override void SetLength(long value)
throw new NotSupportedException();
public override int Read(byte[] buffer, int offset, int count)
if (m_currentBuffer == null)
if (!m_buffers.TryTake(out m_currentBuffer, -1))
return 0;
m_readFromCurrent = 0;
int toRead = Math.Min(count, m_currentBuffer.Length - m_readFromCurrent);
Array.Copy(m_currentBuffer, m_readFromCurrent, buffer, offset, toRead);
m_readFromCurrent += toRead;
if (m_readFromCurrent == m_currentBuffer.Length)
m_currentBuffer = null;
return toRead;
public override void Write(byte[] buffer, int offset, int count)
throw new NotSupportedException();
public override bool CanRead
get return true;
public override bool CanSeek
get return false;
public override bool CanWrite
get return false;
public override long Length
get throw new NotSupportedException();
public override long Position
get throw new NotSupportedException();
set throw new NotSupportedException();
private class WriterStream : Stream
private readonly BlockingCollection<byte[]> m_buffers;
public WriterStream(BlockingCollection<byte[]> buffers)
m_buffers = buffers;
public override void Flush()
public override long Seek(long offset, SeekOrigin origin)
throw new NotSupportedException();
public override void SetLength(long value)
throw new NotSupportedException();
public override int Read(byte[] buffer, int offset, int count)
throw new NotSupportedException();
public override void Write(byte[] buffer, int offset, int count)
if (count == 0)
return;
var copied = new byte[count];
Array.Copy(buffer, offset, copied, 0, count);
m_buffers.Add(copied);
public override bool CanRead
get return false;
public override bool CanSeek
get return false;
public override bool CanWrite
get return true;
public override long Length
get throw new NotSupportedException();
public override long Position
get throw new NotSupportedException();
set throw new NotSupportedException();
protected override void Dispose(bool disposing)
m_buffers.CompleteAdding();
base.Dispose(disposing);
public Stream Reader
get return m_reader;
public Stream Writer
get return m_writer;
不幸的是,您不能从同一个线程同时读取和写入这些流。但是你可以使用Task
从另一个线程写:
XDocument doc = …;
var forwardingStream = new ForwardingStream();
var client = new HttpClient();
var content = new StreamContent(forwardingStream.Reader);
Task.Run(() => doc.Save(forwardingStream.Writer));
var response = client.Post(url, content);
【讨论】:
看起来很多,但大部分只是样板代码。以上是关于使用 HttpClient,如何将 XDocument 直接保存到请求流中?的主要内容,如果未能解决你的问题,请参考以下文章
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