public void Delete( 
   MapMember mapMember,
   IEnumerable<long> oids
)

//must support editing!
//var featSceneLayer = .... ;
if (!featSceneLayer.HasAssociatedFeatureService || 
    !featSceneLayer.IsEditable)
  return;

var delOp = new EditOperation()
{
  Name = "Delete selected features"
};
//Assuming we have a selection on the layer...
delOp.Delete(featSceneLayer, featSceneLayer.GetSelection().GetObjectIDs());
await delOp.ExecuteAsync();//await if needed but not required