Excel interop COM doesn't close

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 applic

Answer 1

1. Use Marshal.FinalReleaseComObject() to release the resources

2. If you read multiple files one after the other then performance wise it is much better to open/close Excel Application only once and move the open/close application part to separate functions

Refactored Code:

static Excel.Application OpenExcel(){
    Excel.Application excel = null;
    try{
        excel = new Excel.Application();
        return excel;
    }
    catch(Exception ex){
        log(ex.Message);
        return null;
    }
}

static void ParseFile(string file)
{
    try
    {
        System.Console.WriteLine("parsing:" + file);            
        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);    
    }
    catch (Exception ex)
    {
        log(ex.Message);
    }
    finally{
        Marshal.FinalReleaseComObject(ws);
        Marshal.FinalReleaseComObject(wb);
        ws = null;
        wb = null;
    }
}

static void CloseExcel(Excel.Application excel){
    try{
        excel.Quit();
    }
    catch(Exception ex){
        log(ex.Message);
    }
    finally{
        Marshal.FinalReleaseComObject(excel);
        excel = null;
    }
}

Usage:

Excel.Application excel = OpenExcel();
if(excel != null){
    // Parse files in a loop
    ParseFile("fileName");

    // Close excel after parsing all files
    CloseExcel(excel);
}