In my last article ‘’, I have explained why we choose to use Excel Application object for excel automation and its disposing mechanism. But, while testing we observed following unexpected behavior:

If we start processing multiple Excel files through windows service (like 25 to 50):

  1. For few files, it threw exception related to COM Interop. The exception does not have any details and it only says ‘File can be accessed’ even though file exists at correct location.
  2. For few files, it starts processing excel file. But the file processing never ends and its associated Excel process was alive too. (You can see ‘Excel’ process in ‘Task Manager’)

There is no solution for above 2 issues (or at least we are not able to find any yet).

So, beware while using Excel Application object in your application!

P.S.: Because of unreliable behavior of Excel Application Objet, we are thinking of using some other third party solution for Excel automation.