ApplicationClass ac = new ApplicationClass();
ac.ShowWindowsInTaskbar = Microsoft.Office.Core.MsoTriState.msoFalse;
....
....
Presentation pptPresentation = ac.Presentations.Open(tempFilePath, Microsoft.Office.Core.MsoTriState.msoFalse, Microsoft.Office.Core.MsoTriState.msoFalse, Microsoft.Office.Core.MsoTriState.msoFalse);
....
.,....
.....
pptPresentation.SaveAs(tempPath, PpSaveAsFileType.ppSaveAsShow, Microsoft.Office.Core.MsoTriState.msoTrue);
pptPresentation.Close();
ac.Quit();
pptPresentation = null;
ac = null;
GC.Collect();