public void Split( 
   Layer layer,
   long oid,
   Geometry splitGeometry
)

var select = MapView.Active.SelectFeatures(clipPoly);

var cutFeatures = new EditOperation();
cutFeatures.Name = "Cut Features";
cutFeatures.Split(featureLayer, oid, cutLine);

//Cut all the selected features in the active view
//Select using a polygon (for example)
//at 2.x - var kvps = MapView.Active.SelectFeatures(polygon).Select(
//      k => new KeyValuePair<MapMember, List<long>>(k.Key as MapMember, k.Value));
//cutFeatures.Split(kvps, cutLine);
var sset = MapView.Active.SelectFeatures(polygon);
cutFeatures.Split(sset, cutLine);

//Execute to execute the operation
//Must be called within QueuedTask.Run
if (!cutFeatures.IsEmpty)
{
  var result = cutFeatures.Execute(); //Execute and ExecuteAsync will return true if the operation was successful and false if not
}

//or use async flavor
//await cutFeatures.ExecuteAsync();

// perform an edit and then a split as one operation.
QueuedTask.Run(() =>
{
  var queryFilter = new QueryFilter();
  queryFilter.WhereClause = "OBJECTID = " + oid.ToString();

  // create an edit operation and name.
  var op = new EditOperation();
  op.Name = "modify followed by split";
  // set the ExecuteMOde
  op.ExecuteMode = ExecuteModeType.Sequential;

  using (var rowCursor = fc.Search(queryFilter, false))
  {
    while (rowCursor.MoveNext())
    {
      using (var feature = rowCursor.Current as Feature)
      {
        op.Modify(feature, "NAME", newName);
      }
    }
  }

  op.Split(layer, oid, splitLine);
  if (!op.IsEmpty)
  {
    bool result = op.Execute();
  }
  // else
  //  The operation doesn't make any changes to the database so if executed it will fail
});