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Releasing Excel after using Interop

, 23 Mar 2011 CPOL
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A small tip how to release Excel object after using Interop

Some time ago, I wrote a simple application to fill in and write on disk an Excel spreadsheet. Something like this:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Office.Interop.Excel;
using System.Net;
using System.IO;
 
namespace ExcelInterop
{
    class Program
    {
        static void Main(string[] args)
        {
            Application oXL = null;
            _Workbook oWB = null;
            Workbooks oWBs = null;
            _Worksheet oSheet = null;
            Range oRange = null;
 
            oXL = new Application();
            oXL.Visible = false;
            oXL.DisplayAlerts = false;
 
            oWBs = oXL.Workbooks;
 
            oWB = oWBs.Add(1);
 
            oSheet = oWB.ActiveSheet;
 
            oRange = oSheet.Cells[1,1];
            oRange.Value = "Test";
 
            oWB.SaveAs(@"C:\Temp\Test.xls", XlFileFormat.xlWorkbookNormal, 
                       null, null, false, false, XlSaveAsAccessMode.xlShared, 
                       false, false, null, null, null);
 
            Console.WriteLine("Before cleanup.");
            Console.ReadKey(false);
 
            oWB.Close();
            oXL.Quit();
 
            System.Runtime.InteropServices.Marshal.ReleaseComObject(oRange);
            System.Runtime.InteropServices.Marshal.ReleaseComObject(oSheet);
            System.Runtime.InteropServices.Marshal.ReleaseComObject(oWB);
            System.Runtime.InteropServices.Marshal.ReleaseComObject(oWBs);
            System.Runtime.InteropServices.Marshal.ReleaseComObject(oXL);
 
            Console.WriteLine("After cleanup.");
            Console.ReadKey(false);
        }
    }
}

Although the program worked as expected, I encountered an annoying problem. The Excel application kept running even after releasing all Interop objects. After some investigation, I realized that the problem was caused by the following two lines of code:

oRange = oSheet.Cells[1,1];
oRange.Value = "Test"

If I comment them out, then after the cleanup, the Excel application will disappear from the list of running processes. But obviously, I needed to set the right value into the cell. So after some Googling, I ended up with the following alternative:

oRange = oSheet.Cells;
oRange.set_Item(1, 1, "Test");

This solution works perfectly, and releases the Excel application after clean up.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Igor Merabishvili
Software Developer (Senior)
Germany Germany
No Biography provided

Comments and Discussions

 
AnswerThank you..... Pinmemberaravinth santosh12-Nov-14 6:54 
QuestionAlternative for Marshal.ReleaseComObject(); PinmemberSuraj S Koneri6-Nov-12 22:24 
GeneralImplicit COM instance is created [modified] Pinmemberwmjordan27-Mar-11 18:55 
GeneralRe: Implicit COM instance is created PinmemberIgor Merabishvili7-Apr-11 0:48 

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