Question

我有三个系列：

private ICollection<FPTAssetClassAsset> wrassets;
private ICollection<FPTFundAsset> wrfunds;
private ICollection<FPTManagedStrategyAsset> wrstrats;

如果foreach循环返回0个对象，则集合不会被设置，因此为null。当我将这个icollection（Union）添加到另一个icollection时，它失败了：“Value不能为null”因为icollection为null，而不是Empty。如何将此集合设置为空？

循环：

    public void GetWrapperAssets(FPT fpt)
    {
        foreach (var w in fpt.CouttsPositionSection.Wrappers
        .Union(fpt.StandAloneSection.Wrappers)
        .Union(fpt.BespokePropositionSection.Wrappers)
        .Union(fpt.NonCouttsPositionSection.Wrappers)
        )
        {
            foreach (var a in w.UnderlyingAssets.OfType<FPTManagedStrategyAsset>())
            {
                wrstrats.Add(a);
            }
            foreach (var a in w.UnderlyingAssets.OfType<FPTAssetClassAsset>())
            {
                wrassets.Add(a);
            }
            foreach (var a in w.UnderlyingAssets.OfType<FPTFundAsset>())
            {
                wrfunds.Add(a);
            }
        }
    }

Answer 1

嗯，您可以在添加之前始终检查null。或者你可以把它变成一个属性：

private ICollection<FPTAssetClassAsset> wrassets
{ 
    get { return _wrassets == null ? new List<FPTAssetClassAsset>() : _wrassets; }
}
private ICollection<FPTAssetClassAsset> _wrassets;

Answer 2

在foreach循环之前初始化你的集合，这样它们总是有一个值：

private ICollection<FPTAssetClassAsset> wrassets = new Collection<FPTAssetClassAsset>();
private ICollection<FPTFundAsset> wrfunds = new Collection<FPTFundAsset>();
private ICollection<FPTManagedStrategyAsset> wrstrats = new Collection<FPTManagedStrategyAsset>();

如何设置空的iCollection c＃

2 个答案: