private void InitGUI()
 {
     if (_searchAvailable == null)
     {
         _searchAvailable = new SearchField();
     }
     if (_availableItems == null)
     {
         _availableItems = new CollectionTreeView();
         _availableItems.ItemDoubleClicked += OnAvailableDoubleClick;
     }
     if (_searchCollection == null)
     {
         _searchCollection = new SearchField();
     }
     if (_collectionItems == null)
     {
         _collectionItems = new CollectionTreeView();
         _collectionItems.ItemDoubleClicked += OnCollectionDoubleClick;
     }
 }