Excel 实例不会在互操作操作后关闭

Question

我正在通过合并一系列不同 Excel 工作簿中的第一个 sheet，用 c# 构建一个新的 Excel 工作簿；随后我将新工作簿导出为 PDF。我完成了这项工作，但在方法结束时总是有一个 Excel 实例运行。

我讨论了同样的问题，但设置更简单，更少我可以使用 GC.Collect 命令解决的 Excel 个对象。现在，none 正在运行。

public void CombineWorkBooks()
    {
        Microsoft.Office.Interop.Excel.Application xlApp = new Microsoft.Office.Interop.Excel.Application();

        xlApp.DisplayAlerts = false;
        xlApp.Visible = false;

        Workbooks newBooks = null;
        Workbook newBook = null;
        Sheets newBookWorksheets = null;
        Worksheet defaultWorksheet = null;

        // Create a new workbook, comes with an empty default worksheet");
        newBooks = xlApp.Workbooks;

        newBook = newBooks.Add(XlWBATemplate.xlWBATWorksheet);
        newBookWorksheets = newBook.Worksheets;

        // get the reference for the empty default worksheet
        if (newBookWorksheets.Count > 0)
        {
            defaultWorksheet = newBookWorksheets[1] as Worksheet;
        }

        // loop through every line in Gridview and get the path' to each Workbook
        foreach (GridViewRow row in CertificadosPresion.Rows)
        {
            string path = row.Cells[0].Text;
            string CertName = CertificadosPresion.DataKeys[row.RowIndex].Value.ToString();

            Workbook childBook = null;
            Sheets childSheets = null;

            // Excel of each line in Gridview
            childBook = newBooks.Open(path,Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing);
            childSheets = childBook.Worksheets;

            if (childSheets != null)
            {
                // Build a new Worksheet
                Worksheet sheetToCopy = null;

                // Only first Worksheet of the Workbook belonging to that line
                sheetToCopy = childSheets[1] as Worksheet;
                if (sheetToCopy != null)
                {
                    // Assign the Certificate Name to the new Worksheet 
                    sheetToCopy.Name = CertName;
                    // set PageSetup for the new Worksheet to be copied
                    sheetToCopy.PageSetup.Zoom = false;
                    sheetToCopy.PageSetup.FitToPagesWide = 1;
                    sheetToCopy.PageSetup.FitToPagesTall = 1;
                    sheetToCopy.PageSetup.PaperSize = Microsoft.Office.Interop.Excel.XlPaperSize.xlPaperA4;
                    // Copy that new Worksheet to the defaultWorksheet
                    sheetToCopy.Copy(defaultWorksheet, Type.Missing);
                }
                System.Runtime.InteropServices.Marshal.ReleaseComObject(sheetToCopy);
                childBook.Close(false, Type.Missing, Type.Missing);
                
            }
            System.Runtime.InteropServices.Marshal.ReleaseComObject(childSheets);
            System.Runtime.InteropServices.Marshal.ReleaseComObject(childBook);
        }

        //Delete the empty default worksheet
        if (defaultWorksheet != null) defaultWorksheet.Delete();

        //Export to PDF
        newBook.ExportAsFixedFormat(Microsoft.Office.Interop.Excel.XlFixedFormatType.xlTypePDF, @"C:\pdf\" + SALESID.Text + "_CertPres.pdf", 0, false, true);

        newBook.Close();
        newBooks.Close();
        xlApp.DisplayAlerts = true;
        DownloadFile(SALESID.Text);

        System.Runtime.InteropServices.Marshal.ReleaseComObject(defaultWorksheet);
        System.Runtime.InteropServices.Marshal.ReleaseComObject(newBookWorksheets);
        System.Runtime.InteropServices.Marshal.ReleaseComObject(newBook);
        System.Runtime.InteropServices.Marshal.ReleaseComObject(newBooks);

        xlApp.Quit();
        System.Runtime.InteropServices.Marshal.ReleaseComObject(xlApp);

        GC.Collect();
        GC.WaitForPendingFinalizers();
    }

        protected void DownloadFile(string Salesid)
    {
        string path = @"c:\pdf\" + Salesid + "_CertPres.pdf";
        byte[] bts = System.IO.File.ReadAllBytes(path);
        Response.Clear();
        Response.ClearHeaders();
        Response.AddHeader("Content-Type", "Application/octet-stream");
        Response.AddHeader("Content-Length", bts.Length.ToString());
        Response.AddHeader("Content-Disposition", "attachment; filename=" + Salesid + "_CertPres.pdf");
        Response.BinaryWrite(bts);
        Response.Flush();
        Response.End();
    }

问题一定与调用下载文件方法有关。我消除了那个调用，并且 Excel 进程被正确关闭。其中一些操作必须保持对其中一个 COM 对象的引用处于打开状态，以便它们无法关闭。通过在 GarbageCollect 之后的最后调用“DownloadFile”，问题就解决了。（我不太清楚为什么）

Answer 1

我发现有时唯一有用的是 "sledgehammer method"。杀死所有运行 excel 个实例：

foreach (Process p in Process.GetProcessesByName("EXCEL"))
{
    try
    {
        p.Kill();
        p.WaitForExit();
    }
    catch
    {
        //Handle exception here
    }
}

Answer 2

在我看来，您有一个未清理的参考。可能类似于 'two dot rule' 问题 - 在我看来这是一个愚蠢的规则，因为你不能编写任何像样的代码，因为它很难跟踪。

您可以尝试 Marshal.ReleaseComObject 个 COM 引用，但仍然自找麻烦...

我的建议是尝试使用 VSTO 实现自动化 Excel。这将代表您正确清除您的引用。

https://social.msdn.microsoft.com/Forums/vstudio/en-US/a12add6b-99ea-4677-8245-cd667101683e/vsto-and-office-objects-disposing

Answer 3

在您的方法 DownloadFile 中，您调用

Response.End()

HttpResponse.End 抛出异常（强调我的）：

To mimic the behavior of the End method in ASP, this method tries to raise a ThreadAbortException exception. If this attempt is successful, the calling thread will be aborted, [...]

此异常中止您的线程。因此，您所有的 ReleaseComObject，Excel.Quit，GC.Collect 东西 永远不会执行 。

解决方法：不要调用 Response.End。你可能不需要它。如果需要，您可能需要考虑替代方案 mentioned in the documentation：

This method is provided only for compatibility with ASP—that is, for compatibility with COM-based Web-programming technology that preceded ASP.NET. If you want to jump ahead to the EndRequest event and send a response to the client, it is usually preferable to call CompleteRequest instead.

[...]

The CompleteRequest method does not raise an exception, and code after the call to the CompleteRequest method might be executed

PS：从 Web 应用程序使用 Excel 自动化是 not officially supported by Microsoft。对于未来的开发，您可能需要考虑使用 third-party Excel 库。

Excel 实例不会在互操作操作后关闭

Excel Instance wont close after Interop Operations

c#

excel

interop