differences between DLL mode and Spawn mode for COM import

Hi All,

I am develop a toolkit program using C/C++ on Creo Parametric 4.0 M090. One of the function is to read a existing excel file. I tried the spawn mode and it works well. The program reads the Excel file cells successfully. But , when I transform my VS project to DLL mode, it stops working. The error information shows that it is failed to initialize COM library with an error code 0x80010106.

Could you give me some help on how to deal with the import COM in DLL mode?

Thanks,

ZR Liu