How to resize the width and height of slide after applying MasterTemplate?

Hi, Support:
How to work this out?
For example:
The Size WxH of the source Slide is 800x600, and the size WxH of the new master template slide is 600x600.
After the new master template slide applied to the source Slide, The Size WxH of the source Slide has been changed to 600x600, my issue is that how recover the size of the handled source Slide back to the original 800x600?
Thanks for your help.

@ducaisoft,
Thank you for your request. You can change the size of presentation slides as below:

presentation.SlideSize.SetSize(800, 600, SlideSizeScaleType.EnsureFit)

Note: Sizing applies to all slides in a presentation by PowerPoint specifications.
API Reference: IPresentation Interface, SlideSizeScaleType Enumeration