如何从后台线程使用FixedDocument？

Question

当所有内容都位于同一个线程上时，下面的代码将正确工作。但是，在将PrintPreview移动到UI线程时，当FixedDocument是在后台线程上生成时，我得到：

“调用线程无法访问此对象，因为其他线程拥有该对象。”

问题是：

writer.Write(fixeddocument.DocumentPaginator);

我无法获得Dispatcher.Invoke/入门调用--或者其他任何解决这个问题的方法。

那么，如何将来自另一个线程的FixedDocument带到UI线程？

(请注意，FixedDocument需要几分钟才能生成，因此必须在后台线程上创建。是的，我在谷歌上搜索了几个小时，没有找到任何解决方案。如果有，我就错过了)。

我一直在想，我必须将PrintPreview保持在与FixedDocument相同的线程中--我希望不会。

// Print Preview
public static void PrintPreview(FixedDocument fixeddocument, CancellationToken ct)
{
    // Was cancellation already requested? 
    if (ct.IsCancellationRequested)
          ct.ThrowIfCancellationRequested();

    MemoryStream ms = new MemoryStream();

    using (Package p = Package.Open(ms, FileMode.Create, FileAccess.ReadWrite))
    {
        Uri u = new Uri("pack://TemporaryPackageUri.xps");
        PackageStore.AddPackage(u, p);

        XpsDocument doc = new XpsDocument(p, CompressionOption.Maximum, u.AbsoluteUri);

        XpsDocumentWriter writer = XpsDocument.CreateXpsDocumentWriter(doc);

        writer.Write(fixeddocument.DocumentPaginator);

        FixedDocumentSequence fixedDocumentSequence = doc.GetFixedDocumentSequence();

        var previewWindow = new PrintPreview(fixedDocumentSequence);

        Action closeAction = () => previewWindow.Close();

        ct.Register(() =>
              previewWindow.Dispatcher.Invoke(closeAction) 
        );

       previewWindow.ShowDialog();  

        PackageStore.RemovePackage(u);
        doc.Close();
    }
}

Answer 1

显然，它是您方法中的static修饰符。将其更改为实例方法允许您方便地使用Dispatcher

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

    }

    // Print Preview
    public void PrintPreview(FixedDocument fixeddocument, CancellationToken ct)
    {
        // Was cancellation already requested? 
        if (ct.IsCancellationRequested)
            ct.ThrowIfCancellationRequested();


        MemoryStream ms = new MemoryStream();

        using (Package p = Package.Open(ms, FileMode.Create, FileAccess.ReadWrite))
        {
            Uri u = new Uri("pack://TemporaryPackageUri.xps");
            PackageStore.AddPackage(u, p);

            XpsDocument doc = new XpsDocument(p, CompressionOption.Maximum, u.AbsoluteUri);

            XpsDocumentWriter writer = XpsDocument.CreateXpsDocumentWriter(doc);

            //writer.Write(fixeddocument.DocumentPaginator);
            Dispatcher.Invoke(new Action<DocumentPaginator>(writer.Write), fixeddocument.DocumentPaginator);

            FixedDocumentSequence fixedDocumentSequence = doc.GetFixedDocumentSequence();

            var previewWindow = new PrintPreview(fixedDocumentSequence);

            Action closeAction = () => previewWindow.Close();

            ct.Register(() =>
                  previewWindow.Dispatcher.Invoke(closeAction)
            );

            previewWindow.ShowDialog();

            PackageStore.RemovePackage(u);
            doc.Close();
        }
    }
}