Get reference to Excel applications using .net and C#

[sclarke2010]

Hi, I have been trying to get a reference to Excel applications using oExcelApp = (Excel.Application)System.Runtime.InteropServices.Marshal.GetActiveObject("Excel.Application"); in C#. This is so that I can use code to automatically save any open workbooks & close the first Excel application, and then do the same for the next Excel application, etc. However unlike the other Office apps (Word, etc) the reference to Excel seems to stay permanently (until the code is finished) ie I can't get the reference to move on to the next Excel application. I have tried killing the Excel app after the first iteration, using threads, etc. Any ideas/thoughts to why this may be happenning?

 

[Legacy 98055]

Are you allowed or willing to use unmanaged code?

 

[sclarke2010]

Hi Tom,

I would prefer managed, but if this only works in unmanaged code then this is fine too.

Do you have some change or suggestion in mind?

Stephen

 

[Colin Legg]

Hi Stephen,

This code (written in C# 4.0) works for me: it closes all Excel instances and saves the open workbooks to my desktop. Mike_R suggested using Process.WaitForExit(), so full credit to him for the idea. If you're using Visual Studio 2008 then you'll have to make some tweaks to get it going...

using System.Diagnostics;
using System.Runtime.InteropServices;
//reference to Excel object library required
using Excel = Microsoft.Office.Interop.Excel;

Two methods:

     Excel.Application GetExcelObject()
     {
         try
         {
             return (Excel.Application)Marshal.GetActiveObject("Excel.Application");
         }
         catch (Exception)
         {
             return null;
         }
     }
 
     Process GetExcelProcess(Excel.Application xlApp)
     {
         Process[] excelProcesses = Process.GetProcessesByName("Excel");
         foreach (Process excelProcess in excelProcesses)
         {
             if (xlApp.Hwnd == excelProcess.MainWindowHandle.ToInt32())
             {
                 return excelProcess;
             }
         }
         throw new InvalidOperationException(
            "Unexplained operation of the 'Process' class: the Excel process could not be returned.");
     }

Then I used a button on a form to execute the procedure:

   private void button1_Click(object sender, EventArgs e)
   {
       const string FilePath = @"C:\Users\Colin\Desktop\";
       const int MaxWait = 60000;
 
       Excel.Application xlApp = GetExcelObject(); 
 
       while (xlApp != null)
       {
           xlApp.DisplayAlerts = false;
           xlApp.EnableEvents = false;
 
           //save and close each workbook
           foreach (Excel.Workbook xlWkb in xlApp.Workbooks)
           {
               string fileExtension;
 
              switch (xlWkb.FileFormat)
               {
                   case Excel.XlFileFormat.xlOpenXMLWorkbook:
                       fileExtension = ".xlsx";
                       break;
                   case Excel.XlFileFormat.xlOpenXMLWorkbookMacroEnabled:
                       fileExtension = ".xlsm";
                       break;
                   default:
                       fileExtension = ".xls";
                       break;
               }
              string fileFullName =
                   FilePath + xlWkb.Name + DateTime.Now.ToString("yy MM dd HHmmss fff") + fileExtension;
               xlWkb.SaveAs(Filename: fileFullName, FileFormat: xlWkb.FileFormat);
               xlWkb.Close(SaveChanges: false);
               Marshal.FinalReleaseComObject(xlWkb);
           }
 
           //Find the currently referenced Excel process so we can be sure when it has been properly killed
           Process xlProcess = GetExcelProcess(xlApp);
 
          // Only need to call GC.Collect() and GC.WaitForPendingFinalizers() once unless using VSTO:
           GC.Collect();
           GC.WaitForPendingFinalizers();
           xlApp.Quit();
           Marshal.FinalReleaseComObject(xlApp);
 
          //wait for the process to completely close before moving on
           xlProcess.WaitForExit(MaxWait);
 
           // Get next Excel.Application object (if available).
           xlApp = GetExcelObject();
       }
       MessageBox.Show("Done!");
   }

 

[sclarke2010]

Thanks for this Colin and Mike. I am away for a few days with intermittent internet access, but will certainly try this when I get back to the office and let you know either way.

Thanks again,

Stephen

 

[sclarke2010]

Hi Colin,

I have now modified the code you sent on in order to work with VS2008 and C#2008, and so that I can call this class in one block so as no user intervention is required.

The code looks fine to me, however when it gets to the end it skips by the second Excel app, as it still hasn't released the first app (even using the WaitForExit(MaxWait) part). I can see this on the task manager. It only releases the originally referenced Excel application properly when the program is stopped, which is too late. I have included the updated code based on your suggestions, so perhaps you could try this to see if it works for you.

I also tried xlProcess.Kill(); rather than xlProcess.WaitForExit(MaxWait); but that didn't make a difference.

Also I wonder if this problem with not releasing the Excel application can be set using some other setting - just a thought?

Regards,

Stephen


using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using System.Diagnostics;
using System.ComponentModel;
using Microsoft.Office.Interop.Excel;
using Excel = Microsoft.Office.Interop.Excel;
using System.Windows.Forms;

namespace Officedocs
{

class Excelproj
{
public Excel.Application oExcelApp = null;
public Workbooks objBooks = null;
public _Workbook objBook = null;

public void ExcelClass()
{
try
{
const string FilePath = @"C:\TEMP\Test\";
const int MaxWait = 6000;
Excel.Application xlApp = GetExcelObject();

while (xlApp != null)
{
xlApp.DisplayAlerts = false;
xlApp.EnableEvents = false;

//save and close each workbook
foreach (Excel.Workbook xlWkb in xlApp.Workbooks)
{
string fileExtension;
switch (xlWkb.FileFormat)
{
case Excel.XlFileFormat.xlOpenXMLWorkbook:
fileExtension = ".xlsx";
break;
case Excel.XlFileFormat.xlOpenXMLWorkbookMacroEnabled:
fileExtension = ".xlsm";
break;
default:
fileExtension = ".xls";
break;
}
string fileFullName = FilePath + xlWkb.Name + DateTime.Now.ToString("yy MM dd HHmmss fff") + fileExtension;
xlWkb.SaveAs(fileFullName, Type.Missing, Type.Missing,
Type.Missing, Type.Missing, Type.Missing,
Excel.XlSaveAsAccessMode.xlNoChange, XlSaveConflictResolution.xlLocalSessionChanges,
true, Type.Missing, Type.Missing, Type.Missing);
xlWkb.Close(true, null, null);
Marshal.FinalReleaseComObject(xlWkb);

}
//Find the currently referenced Excel process so we can be sure when it has been properly killed
Process xlProcess = GetExcelProcess(xlApp);
// Only need to call GC.Collect() and GC.WaitForPendingFinalizers() once unless using VSTO:
GC.Collect();
GC.WaitForPendingFinalizers();
xlApp.Quit();
Marshal.FinalReleaseComObject(xlApp);

//wait for the process to completely close before moving on
xlProcess.WaitForExit(MaxWait);

// Get next Excel.Application object (if available).
xlApp = GetExcelObject();
}
//MessageBox.Show("Done!");
}

catch { }
finally { }
}

Excel.Application GetExcelObject()
{
try
{
return (Excel.Application)Marshal.GetActiveObject("Excel.Application");
}
catch (Exception)
{
return null;
}
}

Process GetExcelProcess(Excel.Application xlApp)
{
Process[] excelProcesses = Process.GetProcessesByName("Excel");
foreach (Process excelProcess in excelProcesses)
{
if (xlApp.Hwnd == excelProcess.MainWindowHandle.ToInt32())
{
return excelProcess;
}
}
throw new InvalidOperationException(
"Unexplained operation of the 'Process' class: the Excel process could not be returned.");
}
}
}

 

[Colin Legg]

Hi Stephen,

The 'good' news is your code works fine for me.

I wonder if this problem with not releasing the Excel application can be set using some other setting - just a thought?

Yes, there are other factors. The next thing I suggest you try is running your code on instances of Excel where no add-ins are running. If it works then you'll know that one of the add-ins is a problem and you can install them one at a time until the problem resurfacess, and then you'll know which one the culprit is.

 

[Zack Barresse]

Moved to appropriate forum.

 

[Tom Black]

I use ZetExcel.

 

[Tom Black]

I use ZetExcel. It is the fastest Excel SDK for .net applications.