如何从Silverlight中的HttpWebRequest.BeginGetRequestStream中更新我的UI

Question

我正在使用HttpWebRequest的BeginGetRequestStream上传多个文件,但我想更新我在发布数据流时编写的进度控件.

应该怎么做,我已经尝试从将数据推送到流中的循环中调用Dispatch.BeginInvoke(如下所示)但是它锁定浏览器直到它完成所以它似乎在某种worker/ui线程死锁中.

这是我正在做的事情的代码片段:

class RequestState
{
    public HttpWebRequest request;  // holds the request
    public FileDialogFileInfo file; // store our file stream data

    public RequestState( HttpWebRequest request, FileDialogFileInfo file )
    {
        this.request = request;
        this.file = file;
    }
}

private void UploadFile( FileDialogFileInfo file )
{
    UriBuilder ub = new UriBuilder( app.receiverURL );
    ub.Query = string.Format( "filename={0}", file.Name );

    // Open the selected file to read.
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create( ub.Uri );
    request.Method = "POST";

    RequestState state = new RequestState( request, file );
    request.BeginGetRequestStream( new AsyncCallback( OnUploadReadCallback ), state );
}

private void OnUploadReadCallback( IAsyncResult asynchronousResult )
{
    RequestState state = (RequestState)asynchronousResult.AsyncState;
    HttpWebRequest request = (HttpWebRequest)state.request;

    Stream postStream = request.EndGetRequestStream( asynchronousResult );
    PushData( state.file, postStream );
    postStream.Close();

    state.request.BeginGetResponse( new AsyncCallback( OnUploadResponseCallback ), state.request );
}

private void PushData( FileDialogFileInfo file, Stream output )
{
    byte[] buffer = new byte[ 4096 ];
    int bytesRead = 0;

    Stream input = file.OpenRead();
    while( ( bytesRead = input.Read( buffer, 0, buffer.Length ) ) != 0 )
    {
        output.Write( buffer, 0, bytesRead );
        bytesReadTotal += bytesRead;

        App app = App.Current as App;
        int totalPercentage = Convert.ToInt32( ( bytesReadTotal / app.totalBytesToUpload ) * 100 );

        // enabling the following locks up my UI and browser
        Dispatcher.BeginInvoke( () =>
        {
            this.ProgressBarWithPercentage.Percentage = totalPercentage;
        } );
    }
}

Answer 1

我想说的是，我不认为 Silverlight 2 的 HttpWebRequest 支持流式传输，因为请求数据完全缓冲到内存中。自从我上次查看它以来已经有一段时间了，因此我回去看看 Beta 2 是否支持它。事实证明确实如此。我很高兴在说出这一点之前我回去阅读了。您可以通过将AllowReadStreamBuffering 设置为 false 来启用它。您是否在 HttpWebRequest 上设置了此属性？这可能会导致你的阻塞。

• MSDN 参考
• Silverlight 和 ASP.NET 的文件上传组件

编辑，为您找到了另一个参考。您可能希望通过将文件分成块来遵循此方法。这是去年 3 月写的，因此我不确定它是否适用于 Beta 2。