public static void SetSnapMode( 
   LayoutSnapMode mode,
   bool value
)

//ensure Element snapping is switched on
LayoutSnapping.SetSnapMode(LayoutSnapMode.Element, true);

// sets only the Guide snapping mode 
ArcGIS.Desktop.Layouts.LayoutSnapping.SetSnapModes(new[] { LayoutSnapMode.Guide });
// sets only Element and Page snapping modes
ArcGIS.Desktop.Layouts.LayoutSnapping.SetSnapModes(new[] { LayoutSnapMode.Element, LayoutSnapMode.Page }); 

// clear all snap modes
ArcGIS.Desktop.Layouts.LayoutSnapping.SetSnapModes(null);


// set snap modes one at a time
ArcGIS.Desktop.Layouts.LayoutSnapping.SetSnapMode(LayoutSnapMode.Margins, true);
ArcGIS.Desktop.Layouts.LayoutSnapping.SetSnapMode(LayoutSnapMode.Guide, true);
/// LayoutSnapping.SetSnapModes(new[]{ LayoutSnapMode.Guide }); // sets only the Guide snapping mode 

// get current snap modes
var snapModes = ArcGIS.Desktop.Layouts.LayoutSnapping.SnapModes;

// get state of a specific snap mode
bool isOn = ArcGIS.Desktop.Layouts.LayoutSnapping.GetSnapMode(LayoutSnapMode.Guide);