properly closing Microsoft.Office.Interop.Excel within c# thread

Question

I've made an application that logs data to an excel file. I can't open the excel file until I've closed the application. In task manager excel.exe is still running after I've closed the excel application in code. I've tried at least 11 ways of closing excel but it doesn't work.

All the code is executed from a thread:

thread = new Thread(() => export_parameters(path));

    public class xlsx_logfile
    {
        private Microsoft.Office.Interop.Excel._Application excel;//excel application that is used for creating excel workbooks(files)
        private Microsoft.Office.Interop.Excel.Workbooks workbooks;
        private Microsoft.Office.Interop.Excel._Workbook workbook;//excel workbook(file)
        private Microsoft.Office.Interop.Excel._Worksheet worksheet;

        private string filename;

        public xlsx_logfile(string path)
        {
            //destructor?

            excel = new Microsoft.Office.Interop.Excel.Application();
            workbooks = excel.Workbooks; 
            workbook = workbooks.Add(Type.Missing);
            worksheet = null;

            worksheet = workbook.ActiveSheet;
            worksheet.Name = "sensordata";

            filename = path;


        }

        public void column_add(uint column_zerobased_index,string header, string format, double[] data)
        {
            Microsoft.Office.Interop.Excel.Range formatRange;

            Microsoft.Office.Interop.Excel.Range c1;
            //Microsoft.Office.Interop.Excel.Range c2;

            column_zerobased_index = 0;

            //var worksheet = workbook.ActiveSheet;



            c1 = worksheet.Cells[1, column_zerobased_index+1];
            //c2 = oSheet.Cells[4, 4];

            formatRange = worksheet.get_Range(c1,c1);//column_zerobased_index + 1
            formatRange.EntireColumn.NumberFormat = "0.0";

            worksheet.Cells[1, column_zerobased_index+1].NumberFormat = "@";
            worksheet.Cells[1, column_zerobased_index + 1] = header;
            //todo use: https://stackoverflow.com/questions/3989122/microsoft-office-interop-excel-really-slow
            for (int i = 0; i < data.Length; ++i)
            {
                worksheet.Cells[i + 1 + 1, column_zerobased_index+1] = data[i];
            }

            // Cleanup
            GC.Collect();
            GC.WaitForPendingFinalizers();
            System.Runtime.InteropServices.Marshal.ReleaseComObject(formatRange);
            System.Runtime.InteropServices.Marshal.ReleaseComObject(c1);
        }

        void close(string filename)
        {
            //worksheet = null;
            //workbook.Close();
            //workbook = null;
            //excel = null;


            //excel.Quit();
            //worksheet = null;
            //workbook = null;
            //excel = null;


            //worksheet = null;
            //workbook.Close();
            //workbook = null;
            //excel.Quit();
            //excel = null;


            //worksheet = null;
            //workbook.Close();
            //workbook = null;


            //var workbooks_local = excel.Workbooks;
            //var workbook_local = workbooks_local.Open(filename);

            //workbook_local.Close();
            //workbooks_local.Close();
            //excel.Quit();

            //System.Runtime.InteropServices.Marshal.ReleaseComObject(workbook_local);
            //System.Runtime.InteropServices.Marshal.ReleaseComObject(workbooks_local);
            //System.Runtime.InteropServices.Marshal.ReleaseComObject(excel);


            //System.Runtime.InteropServices.Marshal.ReleaseComObject(worksheet);
            //worksheet = null;
            ////workbook.Close();
            //System.Runtime.InteropServices.Marshal.ReleaseComObject(workbook);
            //workbook = null;
            ////excel.Quit();
            //System.Runtime.InteropServices.Marshal.ReleaseComObject(excel);
            //excel = null;


            ////based on https://stackoverflow.com/questions/1526685/c-how-can-i-open-and-close-an-excel-workbook
            //workbook.Close(false, filename, null);
            //System.Runtime.InteropServices.Marshal.ReleaseComObject(workbook);
            //excel.Quit();
            //System.Runtime.InteropServices.Marshal.ReleaseComObject(excel);
            //workbook = null;
            //excel = null;
            //GC.Collect();
            //GC.WaitForPendingFinalizers();
            //GC.Collect();
            //GC.WaitForPendingFinalizers();

            //var aap = System.Runtime.InteropServices.Marshal.GetActiveObject("Excel.Application");

            //System.Runtime.InteropServices.Marshal.ReleaseComObject(worksheet);
            //worksheet = null;
            //workbook.Close();
            //System.Runtime.InteropServices.Marshal.ReleaseComObject(workbook);
            //workbook = null;
            //workbooks.Close();
            //System.Runtime.InteropServices.Marshal.ReleaseComObject(workbooks);                
            //workbooks = null;
            //excel.Quit();
            //System.Runtime.InteropServices.Marshal.ReleaseComObject(excel);
            //excel = null;

            // Cleanup
            GC.Collect();
            GC.WaitForPendingFinalizers();

            //System.Runtime.InteropServices.Marshal.FinalReleaseComObject(xlRng);
            System.Runtime.InteropServices.Marshal.FinalReleaseComObject(worksheet);

            workbook.Close(Type.Missing, Type.Missing, Type.Missing);
            System.Runtime.InteropServices.Marshal.FinalReleaseComObject(workbook);

            excel.Quit();
            System.Runtime.InteropServices.Marshal.FinalReleaseComObject(excel);

        }

        public void save()
        {
            workbook.SaveAs(filename);
            close(filename);
        }

    }

edit: this question is different from Closing Excel Application Process in C# after Data Access because I'm executing from a thread, not a method. The provided answers didn't work. I solved the problem myself:

        private Microsoft.Office.Interop.Excel._Application excel;//excel application that is used for creating excel workbooks(files)
        private Microsoft.Office.Interop.Excel._Workbook workbook;//excel workbook(file)
        private Microsoft.Office.Interop.Excel._Worksheet worksheet;

        excel = new Microsoft.Office.Interop.Excel.Application();
        workbook = excel.Workbooks.Add();
        worksheet = workbook.ActiveSheet;

        workbook.Close();
        excel.Quit(); 

        GC.Collect();
        GC.WaitForPendingFinalizers();

        System.Runtime.InteropServices.Marshal.FinalReleaseComObject(worksheet);
        System.Runtime.InteropServices.Marshal.FinalReleaseComObject(workbook);
        System.Runtime.InteropServices.Marshal.FinalReleaseComObject(excel);

        worksheet = null;
        workbook  = null;
        excel     = null;