public FeatureSceneLayerType FeatureSceneLayerType {get;}

{
  if (!featSceneLayer.HasAssociatedFeatureService)
    return;//Search and Select not supported

  //Multipatch (Object3D) or point?
  //var is3dObject = ((ISceneLayerInfo)featSceneLayer).SceneServiceLayerType 
  //                                  == esriSceneServiceLayerType.Object3D;
  var is3dObject = featSceneLayer.FeatureSceneLayerType == FeatureSceneLayerType.Object3D;
  // Note: call within QueuedTask.Run()
  {
    var queryFilter = new QueryFilter
    {
      WhereClause = "Name = 'Ponderosa Pine'",
      SubFields = "*"
    };

    int rowCount = 0;
    //or select... var select = featSceneLayer.Select(queryFilter)
    using (RowCursor rowCursor = featSceneLayer.Search(queryFilter))
    {
      while (rowCursor.MoveNext())
      {
        using (var feature = rowCursor.Current as Feature)
        {
          oid = feature.GetObjectID();
          var shape = feature.GetShape();
          var attrib = feature["Name"];
          if (is3dObject)
          {
            //shape is a multipatch
          }
          else
          {
            //shape is a point
          }
          rowCount += 1;
        }
      }
    }
  }
}