Inheritance: BaseVM
 public ExplorerVM(MainVM main)
 {
     this._main = main;
     this.RootItems = new ObservableCollection<ExplorerItemBaseVM>();
 }
 public ExplorerVM(MainVM main)
 {
     this._main     = main;
     this.RootItems = new ObservableCollection <ExplorerItemBaseVM>();
 }