c# - Automatically exit generated Excel file correctly

My program generates an Excel in a loop and sends it by Email. In each loop iteration it should overwrite the Excel, but the Excel is still used by the old Excel process which is why I get a System.IO.IOException exception.

Here is the process:

Here is the Code:

if(File.Exists(PfadXlsx)) File.Delete(PfadXlsx);
        mExcel.Visible = true;
        mExcelWs.SaveAs(PfadXlsx, Microsoft.Office.Interop.Excel.XlFileFormat.xlWorkbookDefault, missing, missing, false, false, false, missing, missing, missing);     // Datei speichern
        mExcelWb.Close(true, missing, missing);
        mExcel.Application.Quit();
        mExcel.Quit();

mExcel == Excel.Application mExcelWB == Excel.Workbook
mExcel==Excel.Worksheet missing == type.missing