C#

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");
                }
            }
        }