public static void SetSnapMode( 
   SnapMode mode,
   bool value
)

// set only Point and Edge snapping modes, clear everything else
//At 2.x - ArcGIS.Desktop.Mapping.Snapping.SetSnapModes(SnapMode.Point, SnapMode.Edge);
ArcGIS.Desktop.Mapping.Snapping.SetSnapModes(
  new List<SnapMode>() { SnapMode.Point, SnapMode.Edge });

// clear all snap modes
//At 2.x - ArcGIS.Desktop.Mapping.Snapping.SetSnapModes();
ArcGIS.Desktop.Mapping.Snapping.SetSnapModes(null);


// set snap modes one at a time
ArcGIS.Desktop.Mapping.Snapping.SetSnapMode(SnapMode.Edge, true);
ArcGIS.Desktop.Mapping.Snapping.SetSnapMode(SnapMode.End, true);
ArcGIS.Desktop.Mapping.Snapping.SetSnapMode(SnapMode.Intersection, true);

// get current snap modes
var snapModes = ArcGIS.Desktop.Mapping.Snapping.SnapModes;

// get state of a specific snap mode
bool isOn = ArcGIS.Desktop.Mapping.Snapping.GetSnapMode(SnapMode.Vertex);

// interested in only snapping to the vertices of a specific layer of interest and not the vertices of other layers
//  all other snapModes should be off.

// snapping must be on
ArcGIS.Desktop.Mapping.Snapping.IsEnabled = true;

// turn all application snapModes off
//At 2.x - ArcGIS.Desktop.Mapping.Snapping.SetSnapModes();
ArcGIS.Desktop.Mapping.Snapping.SetSnapModes(null);

// set application snapMode vertex on 
ArcGIS.Desktop.Mapping.Snapping.SetSnapMode(SnapMode.Vertex, true);

// ensure layer snapping is on
await QueuedTask.Run(() =>
{
  fLayer.SetSnappable(true);
});

// set vertex snapping only
var vertexOnly = new LayerSnapModes(false);
vertexOnly.Vertex = true;

// set vertex only for the specific layer, clearing all others
var dict = new Dictionary<Layer, LayerSnapModes>();
dict.Add(fLayer, vertexOnly);
ArcGIS.Desktop.Mapping.Snapping.SetLayerSnapModes(dict, true);  // true = reset other layers