不用担心List没有创建问题。
private ObservableCollection<EquipmentItem> _optionalCollection;public ObservableCollection<EquipmentItem> OptionalCollection{get{if (this._optionalCollection == null){this._optionalCollection = new ObservableCollection<EquipmentItem>();}return this._optionalCollection;}set{if (value != this._optionalCollection){if (this._optionalCollection != null){this._optionalCollection.Clear();}this._optionalCollection = value;this.RaisePropertyChangedEvent("OptionalCollection");}}}