Question

I have some code that opens a spreadsheet, reads some values, and then closes the sheet. I need to do this for multiple files. The problem I’m having is that the Excel application instance is not exiting, therefore when I run my process for several files, I end up with several excel.exe processes running. Any ideas how I get Excel to close?

    static void ParseFile(string file)
    {
        try
        {
            System.Console.WriteLine("parsing:" + file);
            Excel.Application excel = new Excel.Application();
            Excel.Workbook wb = excel.Workbooks.Open(file);
            Excel.Worksheet ws = wb.Worksheets[1];
            for (int i = 2; i < 27; i++)
            {
                log(ws.Cells[i, 1].Text);
            }
            wb.Close(false);                
            excel.Quit();
            excel = null;
            ws = null;
            wb = null;
        }
        catch (Exception ex)
        {
            log(ex.Message);
        }
    }

——Update 12/11/12——–Still leaving excel instances open——-

static void ParseFile(string file)
    {
        try
        {
            log("parsing:" + file);
            Excel.Application excel = new Excel.Application();
            Excel.Workbook wb = excel.Workbooks.Open(file);
            Excel.Worksheet ws = wb.Worksheets[1];
    //do some stuff here
            wb.Close(false);
            excel.Quit();
            GC.Collect();
            GC.WaitForPendingFinalizers();
            Marshal.FinalReleaseComObject(ws);
            Marshal.FinalReleaseComObject(wb);
            Marshal.FinalReleaseComObject(excel);                
            excel = null;
            ws = null;
            wb = null;
            System.GC.Collect();
        }
        catch (Exception ex)
        {
            log(ex.Message);
        }            
    }

Answer 1

Ended up killing the processes, that was the only thing that worked.

    [DllImport("user32.dll")]
    private static extern uint GetWindowThreadProcessId(IntPtr hWnd, out uint lpdwProcessId);

    /// <summary> Tries to find and kill process by hWnd to the main window of the process.</summary>
    /// <param name="hWnd">Handle to the main window of the process.</param>
    /// <returns>True if process was found and killed. False if process was not found by hWnd or if it could not be killed.</returns>
    public static bool TryKillProcessByMainWindowHwnd(int hWnd)
    {
        uint processID;
        GetWindowThreadProcessId((IntPtr)hWnd, out processID);
        if (processID == 0) return false;
        try
        {
            Process.GetProcessById((int)processID).Kill();
        }
        catch (ArgumentException)
        {
            return false;
        }
        catch (Exception ex)
        {
            return false;
        }            
        return true;
    }

    static void ParseFile(string file)
    {
        try
        {
            log("parsing:" + file);
            Excel.Application excel = new Excel.Application();
            Excel.Workbook wb = excel.Workbooks.Open(file);
            Excel.Worksheet ws = wb.Worksheets[1];
            //do some stuff here
            wb.Close(false);
            int hWnd = excel.Application.Hwnd;
            excel.Quit();
            GC.Collect();
            GC.WaitForPendingFinalizers();
            GC.Collect();
            GC.WaitForPendingFinalizers();
            Marshal.FinalReleaseComObject(ws);
            Marshal.FinalReleaseComObject(wb);
            Marshal.FinalReleaseComObject(excel);                
            excel = null;
            ws = null;
            wb = null;
            GC.Collect();
            GC.WaitForPendingFinalizers();
            GC.Collect();
            GC.WaitForPendingFinalizers();
            TryKillProcessByMainWindowHwnd(hWnd);
        }
        catch (Exception ex)
        {
            log(ex.Message);
        }            
    }