End Google Ads 201810 - BS.net 01 --> Hello there,

I wrote a tool for importing and exporting data into ExcelSheets (better said: workbooks).

Some relevant parts of my code are:
using Excel = Microsoft.Office.Interop.Excel;
Excel.ApplicationClass excelApp = new Excel.ApplicationClass();
excelApp.ScreenUpdating = false;
excelApp.DisplayAlerts = false;

then I open some workbooks, open some sheets, write some stuff into them and close all of them. I also dereference them if they are no more needed (mysheet = null).
But after finally shutting down the ExcelApp doing so:
excelApp.Quit();
excelApp = null;

... I have to wait quite a long time (about half a minute) until I see the EXCEL-thread diappear in my ProcessExplorer.
The problem is, that I can not open the just written xls-files if the application did not end, because it still has got its hands on the files.
So I have to know when this happens.

My questions are:
Why does it take so long?
When does the Excel-thread really end?
How do I end it correctly?
How can I provoke the thread to be ended?
Or is it just a matter of garbage collection? (a field I did not yet explore)

Thanks in advance,
Harry

no plan,
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