public static List<LayoutSnapMode> SnapModes {get; set;}

//Get the current snapping modes
foreach (var snappingMode in LayoutSnapping.SnapModes)
  { ... } // do something for currently set snapping modes
  
//Set the current snapping modes
var modes = LayoutSnapping.SnapModes;
LayoutSnapping.SnapModes = modes;

// 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);