This adds an #Extension method to #Object (necessary as there are loads of different types of COM object, but with no more specific superclass other than Object) which will properly release a #COM object. This is oriented towards #Excel so it includes code to close workbooks, and properly quit Excel Applications - could easily be extended with a…

COM_ObjectExtensions.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Excel = Microsoft.Office.Interop.Excel;

namespace AnalysisSuite.Extensions
{
    public static class ObjectExtensions
    {
        public static void CloseReleaseAndNullComObject(this object o)
        {
            //http://support.microsoft.com/kb/317109
            try
            {
                if ((o as Excel.Workbook) !=null) ((Excel.Workbook)o).Close();
                if ((o as Excel.Workbooks) != null) ((Excel.Workbooks)o).Close();
                if ((o as Excel._Application) != null)
                {
                    ((Excel._Application)o).Visible = true;
                    ((Excel._Application)o).ScreenUpdating = true;
                    ((Excel._Application)o).DisplayAlerts = true;
                    ((Excel._Application)o).Quit();
                }
                System.Runtime.InteropServices.Marshal.FinalReleaseComObject(o);
            }
            catch { }
            finally
            {
                o = null;
            }
        }
    }
}