Question

我已经在这周围敲打了一段时间（并且知道这是愚蠢的事情）。

我使用ProgressBar下载文件时显示正常，但如何从ReadAsync流中获取数据以保存？

public static readonly int BufferSize = 4096;
int receivedBytes = 0;
int totalBytes = 0;
WebClient client = new WebClient();
byte[] result;

using (var stream = await client.OpenReadTaskAsync(urlToDownload))
{
  byte[] buffer = new byte[BufferSize];
  totalBytes = Int32.Parse(client.ResponseHeaders[HttpResponseHeader.ContentLength]);

  for (;;)
  {
    result = new byte[stream.Length];
    int bytesRead = await stream.ReadAsync(buffer, 0, buffer.Length);
    if (bytesRead == 0)
    {
      await Task.Yield();
      break;
    }

    receivedBytes += bytesRead;
    if (progessReporter != null)
    {
      DownloadBytesProgress args = 
                 new DownloadBytesProgress(urlToDownload, receivedBytes, totalBytes);
      progessReporter.Report(args);
    }
  }
}

我正在尝试通过结果var，但这显然是错误的。在这个漫长的周日下午，我感激不尽。

Answer 1

下载的内容位于byte[] buffer变量中：

int bytesRead = await stream.ReadAsync(buffer, 0, buffer.Length);

来自Stream.ReadAsync：

缓冲液：

类型：System.Byte []   将数据写入的缓冲区。

您根本不会使用result变量。不知道为什么会这样。

修改

所以问题是如何阅读流的完整内容。您可以执行以下操作：

public static readonly int BufferSize = 4096; int receivedBytes = 0; WebClient client = new WebClient(); using (var stream = await client.OpenReadTaskAsync(urlToDownload)) using (MemoryStream ms = new MemoryStream()) { var buffer = new byte[BufferSize]; int read = 0; totalBytes = Int32.Parse(client.ResponseHeaders[HttpResponseHeader.ContentLength]); while ((read = await stream.ReadAsync(buffer, 0, buffer.Length)) > 0) { ms.Write(buffer, 0, read); receivedBytes += read; if (progessReporter != null) { DownloadBytesProgress args = new DownloadBytesProgress(urlToDownload, receivedBytes, totalBytes); progessReporter.Report(args); } } return ms.ToArray(); } }

Answer 2

您阅读的数据应位于buffer数组中。实际上是数组的起始bytesRead个字节。检查MSDN上的ReadAsync方法。

ReadAsync从缓冲区获取数据

2 个答案: