Power Point automation using Microsoft.Office.Interop.PowerPoint Ms office COM interop is quite easy for most of the use cases. But many of methods are undocumented or documentation is not sufficient. Below is example of code to end slide show using c-Sharp.

//Initialize power point application object
//as you want
//Below is just for reference
Microsoft.Office.Interop.PowerPoint.Application app =
new Microsoft.Office.Interop.PowerPoint.Application();

app.ActivePresentation.SlideShowWindow.View.Exit();
//Do cleanup 

ActivePresentation.SlideShowWindow.View.Exit() is used to end slide show.