C# Excel Process persisting

Question

I have a C# application that exports a lot of data to Excel. I leave the Excel app open so the user can decide what they want to do with it. However, when Excel is shut down (directly from within Excel), there is still an Excel process hanging around that has to be manually killed.

I guess a solution is to save the data in Excel and shut it down from within my code using Marshal thus leaving no Excel apps hanging around, but my users want the file open to them when they export data.

Has anyone found a way around the zombie processes?

Answer 1

Once I made the class below. It's a while ago and I haven't used it recently so don't hang me if it doesn't work. Feel free to use, change, be inspired or neglect it as you see fit.

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices;
using System.Threading;
using Excel = Microsoft.Office.Interop.Excel;

namespace ExcelHandlingTest
{
  public class ExcelManager : IDisposable
  {
    Excel.Application m_excelApp = null;
    Process m_excelProcess = null;
    bool m_closeOnDispose = false;
    bool m_allowKillAll = false;

    public ExcelManager(bool useExistingInstance, bool closeOnDispose, bool visible, bool allowKillAll = false)
    {
      m_closeOnDispose = closeOnDispose;
      m_allowKillAll = allowKillAll;

      if (useExistingInstance)
      {
        try
        {
          m_excelApp = Marshal.GetActiveObject("Excel.Application") as Excel.Application;
        }
        catch (COMException ex)
        {
          m_excelApp = new Excel.Application();
        }
      }
      else
      {
        m_excelApp = new Excel.Application();
      }
      if (m_excelApp == null)
        throw new Exception("Excel may not be present on this machine");

      m_excelApp.Visible = visible;

      SetExcelProcess();
    }

    public Excel.Application Excel
    {
      get
      {
        return m_excelApp;
      }
    }

    [DllImport("User32.dll")]
    private static extern uint GetWindowThreadProcessId(IntPtr hwnd, out uint lpdwProcessId);

    private void SetExcelProcess()
    {
      uint processId = 0;
      GetWindowThreadProcessId((IntPtr)m_excelApp.Hwnd, out processId);
      m_excelProcess = Process.GetProcessById((int)processId);
    }

    private static List<int> GetExcelProcessIds()
    {
      return GetAllExcelProcesses().Select(p => p.Id).ToList();
    }

    public static void KillAllExcelProcesses()
    {
      foreach (Process p in GetAllExcelProcesses())
      {
        p.Kill();
      }
    }

    public static List<Process> GetAllExcelProcesses()
    {
      return (from p in Process.GetProcessesByName("Excel")
              where Path.GetFileName(p.MainModule.FileName).Equals("Excel.exe", StringComparison.InvariantCultureIgnoreCase) &&
              p.MainModule.FileVersionInfo.CompanyName.Equals("Microsoft Corporation", StringComparison.InvariantCultureIgnoreCase)
              select p).ToList();
    }

    public event ExitStatusEventHandler ExitStatus;
    private void OnExitStatus(string status)
    {
      if (ExitStatus != null)
        ExitStatus(this, status);
    }

    public void Dispose()
    {
      if (m_excelProcess != null)
        OnExitStatus(string.Format("Process ID: {0}", m_excelProcess.Id));

      if (m_closeOnDispose)
      {
        if (m_excelApp != null)
          m_excelApp.Quit();
        m_excelApp = null;
        GC.Collect();
        GC.WaitForPendingFinalizers();
        Thread.Sleep(50);

        if (m_excelProcess != null)
        {
          List<Process> excelProcs = GetAllExcelProcesses();
          foreach (Process ep in excelProcs)
          {
            if (ep.MainWindowHandle == m_excelProcess.MainWindowHandle)
            {
              ep.Kill();
              ep.WaitForExit();
              OnExitStatus("Exit by Kill");
              m_excelProcess = null;
              return;
            }
          }
        }

        if (m_allowKillAll)
        {
          List<Process> excelProcs = GetAllExcelProcesses();
          if (excelProcs != null && excelProcs.Count > 0)
          {
            KillAllExcelProcesses();
            OnExitStatus("Exit by Kill All");
            m_excelProcess = null;
            return;
          }
        }

        OnExitStatus("Exit by Quit");
        m_excelProcess = null;
      }
    }
  }

  public delegate void ExitStatusEventHandler(ExcelManager sender, string status);
}

Use case:

  using (ExcelManager man = new ExcelManager(true, true, true))
  {
    var excel = man.Excel;
    // do stuff..
  }