Question

我正在尝试在复制文件时实现进度通知机制。我是按照以下方式做到的：

我创建了两个FileStream - 用于读写
调用 BeginRead 向其传递 ReadCallback 以及包含读取流和数组的结构，以填充从文件中读取的数据。
在 ReadCallback 中，我调用 EndRead 方法并在用于写入的文件流上调用 BeginWrite 方法传递给它 WriteCallback 以及包含流（用于写入）和要写入的数组的结构（与读取部分相同）。
当我在 WriteCallback 中调用 EndWrite 传递给它时，asyncResult会抛出 ArgumentException：IAsyncResult对象不是来自相应的异步方法在此类型上，或者使用相同的IAsyncResult

请帮忙解决此问题。

更新源代码：

private void StartAsyncCopying()
{
    var sourceFileInfo = new FileInfo(Source);
    if (!sourceFileInfo.Exists)
    {
        throw new FileNotFoundException("File not found.",
            Source);
    }
    m_sourceLength = sourceFileInfo.Length;
    m_readerStream = new FileStream(Source, FileMode.Open);
    m_writerStream = new FileStream(Target, FileMode.Create);
    m_queueBuffer = new Queue<byte[]>(DefaultQueueBufferSize);
    m_queueBufferLock = new object();

    ProgressRead();
}

private void ProgressRead()
{
    var readerChunck = new byte[DefaultChunckSize];
    var streamChunck = new StreamChunck(readerChunck, m_readerStream);
    m_readerStream.BeginRead(streamChunck.Chunck,
        0,
        streamChunck.Chunck.Length,
        ReadCallback,
        streamChunck);
}


private void ReadCallback(IAsyncResult asyncResult)
{
    var streamChunck = asyncResult.AsyncState as StreamChunck;
    var numberOfBytesRead = streamChunck.Stream.EndRead(asyncResult);

    m_readerOffset += numberOfBytesRead;

    ProgressWrite(streamChunck.Chunck);
}

private void ProgressWrite(byte[] chunck)
{
    var streamChunck = new StreamChunck(chunck, m_writerStream);
    m_writerAsyncResult = m_writerStream.BeginWrite(streamChunck.Chunck,
        0,
        streamChunck.Chunck.Length,
        WriteCallback,
        streamChunck);
}

private void WriteCallback(IAsyncResult asyncResult)
{
    var streamChunck = asyncResult.AsyncState as StreamChunck;
    var numberOfBytesWritten = streamChunck.Stream.EndRead(asyncResult);
    m_writerOffset += numberOfBytesWritten;

    var progressChangedEventArgs = new CopyProgressChangedEventArgs(m_operationDescription,
        m_sourceLength,
        m_writerOffset);
    OnCopyProgressChanged(progressChangedEventArgs);

    if (m_writerOffset == m_sourceLength)
    {
        var copyCompletedEventArgs = new CopyCompletedEventArgs(m_operationDescription, null);
        OnCopyCompleted(copyCompletedEventArgs);
    }
    else
    {
        ProgressRead();
    }
}

Answer 1

当您致电BeginXXX时，您可能会收到IAsyncResult个对象，要拨打EndXXX，您需要将此IAsyncResult引用传递给该方法。如果您使用了Read中的相同对象并将其传递给Write，则它将无法工作 - 在您的场景中将有两个单独的IAsyncResult对象。

当我这样做时，我将对返回的IAsyncResult的引用保留为本地类变量（如果使用回调）。当我致电EndXXX时，我会提供此本地参考（从我的初始BeginXXX获得）并在之后将其归零以表示它可以重复使用。

更新2：查看您的代码，EndWrite中的WriteCallback实际上是EndRead，野餐错误： - ）

更新1：以下对我来说很好......

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

namespace ConsoleApplication14
{
    class Program
    {
        static FileStream fs = null;
        static MemoryStream ms = null;
        static byte[] buffer = new byte[512];

        static void Main(string[] args)
        {
            fs = new FileStream("theFile", FileMode.Open);
            fs.BeginRead(buffer, 0, 512, new AsyncCallback(ReadFinished), null);

            Console.Read();
        }

        static void ReadFinished(IAsyncResult res)
        {
            fs.EndRead(res);
            fs.Dispose();

            ms = new MemoryStream();
            ms.BeginWrite(buffer, 0, 512, new AsyncCallback(WriteFinished), null);
        }

        static void WriteFinished(IAsyncResult res)
        {
            ms.EndWrite(res);
            ms.Dispose();
        }
    }
}

Answer 2

你有以下内容：

private void WriteCallback(IAsyncResult asyncResult)
{
    var streamChunck = asyncResult.AsyncState as StreamChunck;
    var numberOfBytesWritten = streamChunck.Stream.EndRead(asyncResult);
                                                   ^^^^^^^

但你正在写作。你不应该打电话给EndWrite吗？或者我错过了一些非常明显的东西？

该方法中也有ProgressRead();。

FileStream.EndWrite抛出异常（.NET）

2 个答案: