Question

我有这个奇怪的问题。

我主线上的代码：

WebClient client = new WebClient();
client.OpenReadCompleted += new OpenReadCompletedEventHandler((ss, ee) =>
{
    Dispatcher.BeginInvoke(() =>
    {
        try
        {
            BitmapImage bi = new BitmapImage();
            bi.SetSource(ee.Result);
            WriteableBitmap wb = new WriteableBitmap(bi);
            _okAction.Invoke(linkTexBox.Text, wb);

            theProgressBarDialog.Close();
        }
        catch (Exception)
        {
            theProgressBarDialog.Close();

            string msg = "Cannot fetch the image.  Please make sure the image URL is correct";
            MessageBox.Show(msg);
        }
    });
});
client.OpenReadAsync(new Uri("Image URL without cross domain problem"));
theProgressBarDialog.Show();

图像已成功加载，并在我的画布上呈现。

奇怪的行为有时候，我的整个Silverlight应用程序看起来都很冷，应用程序不会响应任何用户操作，除非右键单击，弹出默认的Silverlight上下文菜单。

强制禁用按钮。

调试时，不会抛出任何异常。

编辑：如果我设置client.AllowReadStreamBuffering = false，我将获得例外：

{System.NotSupportedException: Read is not supported on the main thread when buffering is disabled.
   at MS.Internal.InternalNetworkStream.Read(Byte[] buffer, Int32 offset, Int32 count)
   at System.Windows.Media.Imaging.BitmapSource.ReadStream(Stream streamSource, Byte[]& buffer, Int32& position)
   at System.Windows.Media.Imaging.BitmapSource.SetSourceInternal(Stream streamSource)
   at System.Windows.Media.Imaging.BitmapImage.SetSourceInternal(Stream streamSource)
   at System.Windows.Media.Imaging.BitmapSource.SetSource(Stream streamSource)
   at ToonGui.ImportImageDialog.<>c__DisplayClass2.<OKButton_Click>b__1()}
    [System.NotSupportedException]: {System.NotSupportedException: Read is not supported on the main thread when buffering is disabled.
   at MS.Internal.InternalNetworkStream.Read(Byte[] buffer, Int32 offset, Int32 count)
   at System.Windows.Media.Imaging.BitmapSource.ReadStream(Stream streamSource, Byte[]& buffer, Int32& position)
   at System.Windows.Media.Imaging.BitmapSource.SetSourceInternal(Stream streamSource)
   at System.Windows.Media.Imaging.BitmapImage.SetSourceInternal(Stream streamSource)
   at System.Windows.Media.Imaging.BitmapSource.SetSource(Stream streamSource)
   at ToonGui.ImportImageDialog.<>c__DisplayClass2.<OKButton_Click>b__1()}
    Data: {System.Collections.ListDictionaryInternal}
    InnerException: null
    Message: "Read is not supported on the main thread when buffering is disabled."
    StackTrace: "   at MS.Internal.InternalNetworkStream.Read(Byte[] buffer, Int32 offset, Int32 count)\r\n   at System.Windows.Media.Imaging.BitmapSource.ReadStream(Stream streamSource, Byte[]& buffer, Int32& position)\r\n   at System.Windows.Media.Imaging.BitmapSource.SetSourceInternal(Stream streamSource)\r\n   at System.Windows.Media.Imaging.BitmapImage.SetSourceInternal(Stream streamSource)\r\n   at System.Windows.Media.Imaging.BitmapSource.SetSource(Stream streamSource)\r\n   at ToonGui.ImportImageDialog.<>c__DisplayClass2.<OKButton_Click>b__1()"

我是否必须使用BackgroundWorker类让下载任务在另一个线程中运行？

Answer 1

谢谢你们，我终于找到了答案。这是一个Siverlight错误，这是微软的错。

正如我的一位朋友所说微软。。。总是有一堆令人想杀人的问题（意思是Microsoft.... always has some issues that drive you crazy enough so that you want to shoot someone）

原因来自theProgressBarDialog，这是一个ChildWindow，这是一个愚蠢的错误：关闭后，有时会让父窗口（主应用程序）被禁用。

Silverlight：Modal ChildWindow在关闭后保持父灰色：（也可以尝试调用this.DialogResult = true而不是Close方法。） Silverlight: Modal ChildWindow keeps parent grayed after closing
Silverlight 4 ChildWindow在关闭后将父级禁用： http://social.msdn.microsoft.com/Forums/en-US/silverlightbugs/thread/56d0dc0b-3711-4643-b56f-2c94344e3d3a/

解决方案是：

        private void ChildWindow_Closed(object sender, System.EventArgs e)
        {
// TODO: should we use apply this fix to all ChildWindow? (make a TnChildWindow)
//   1. Silverlight: Modal ChildWindow keeps parent grayed after closing:
//      (Also try calling this.DialogResult = true instead of the Close method.)
//      https://stackoverflow.com/questions/6456952/silverlight-modal-childwindow-keeps-parent-grayed-after-closing
//   2. Silverlight 4 ChildWindow leaves parent disabled after closing:
//      http://social.msdn.microsoft.com/Forums/en-US/silverlightbugs/thread/56d0dc0b-3711-4643-b56f-2c94344e3d3a/
            Application.Current.RootVisual.SetValue(Control.IsEnabledProperty, true);
        }

使用WebClient加载图像时Silverlight应用程序几乎冻结（ChildWindow用作ProgressBar）

1 个答案: