Question

[请注意：此问题在我的其他问题中得到了有效解决：How to use a cancellationtokensource to cancel background printing]

我一直在使用以下方法（来自SO）来运行我的打印机并在后台线程上打印预览：

 public static Task StartSTATask(Action func)
        {
            var tcs = new TaskCompletionSource<object>();
            var thread = new Thread(() =>
            {
                try
                {
                    func();
                    tcs.SetResult(null);
                }
                catch (Exception e)
                {
                    tcs.SetException(e);
                }
            });
            thread.SetApartmentState(ApartmentState.STA);

            thread.Priority = ThreadPriority.AboveNormal;
            thread.Start();
            return tcs.Task;
        }

它完美无缺，没有错误。

我不知道如何正确取消此任务。我应该完全中止线程还是传入CancellationTokenSource令牌？如何更改上述代码以允许取消（或中止）？

我很困惑。感谢您对此的任何帮助。

（经过大量的谷歌搜索，这里的解决方案根本不像我希望的那样微不足道！）

经过深思熟虑后，我倾向于将CancellationToken传递给正在执行的func（），并强制终止该函数。在这种情况下，这意味着要关闭PrintDialogue（）。还有另外一种方法吗？

我正在使用上面的代码：

 public override Task PrintPreviewAsync()
    {
            return StartSTATask(() =>
            {
                // Set up the label page
                LabelMaker chartlabels =  ...

                ... create a fixed document...

                // print preview the document.
                chartlabels.PrintPreview(fixeddocument);
            });
        }

// Print Preview
    public static void PrintPreview(FixedDocument fixeddocument)
    {
        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);

            /*  A Working Alternative without custom previewer
            //View in the DocViewer
            var previewWindow = new Window();
            var docViewer = new DocumentViewer();  //  the System.Windows.Controls.DocumentViewer class.
            previewWindow.Content = docViewer;

            FixedDocumentSequence fixedDocumentSequence = doc.GetFixedDocumentSequence();
            docViewer.Document = fixedDocumentSequence as IDocumentPaginatorSource;

            // ShowDialog - Opens a window on top and returns only when the newly opened window is closed.
            previewWindow.ShowDialog();
            */

            FixedDocumentSequence fixedDocumentSequence = doc.GetFixedDocumentSequence();

            // Use my custom document viewer (the print button is removed).
            var previewWindow = new PrintPreview(fixedDocumentSequence);
            previewWindow.ShowDialog();
            PackageStore.RemovePackage(u);
            doc.Close();
        }
    }

希望它有助于更好地解释我的问题。

如何正确取消在后台STA线程上运行的打印任务？

0 个答案: