c# - 更新列表列表中的属性

Question

问题是:如何在不循环的情况下更新 allItems 中的字段 ItemCount(例如，使用 Linq)？例如，如果 Index = 0，我想将 ItemCount 设置为 ItemCount-5。

你可以看到下面的代码。

我有以下类(class):

public class Item
{
    private int index;
    private string item_name;
    private double item_count;
    private string type_name;

    public int Index
    {
        get { return index; }
        set { index = value; }
    }
    public string ItemName
    {
        get { return item_name; }
        set { item_name = value; }
    }
    public double ItemCount
    {
        get { return item_count; }
        set { item_count = value; }
    }
    public string TypeName
    {
        get { return type_name; }
        set { type_name = value; }
    }

}

public class CombMin
{
    private double min_count;
    private List<Item> combination;

    public double MinCount
    {
        get { return min_count; }
        set { min_count = value; }
    }
    public List<Item> Combination
    {
        get { return combination; }
        set { combination = value; }
    }
}

然后我创建了 List allItems:

        var item1 = new Item { Index=0,ItemName="x1",ItemCount=104,TypeName="Type1" };
        var item2 = new Item { Index = 1, ItemName = "x2", ItemCount = 104, TypeName = "Type1" };
        var item3 = new Item { Index = 2, ItemName = "x3", ItemCount = 1495, TypeName = "Type1" };
        var item4 = new Item { Index = 0, ItemName = "x1", ItemCount = 104, TypeName = "Type1" };
        var item5 = new Item { Index = 1, ItemName = "x2", ItemCount = 104, TypeName = "Type1" };
        var item6 = new Item { Index = 2, ItemName = "x3", ItemCount = 1495, TypeName = "Type1" };

        var items1 = new List<Item>();
        var items2 = new List<Item>();
        items1.Add(item1);
        items1.Add(item2);
        items1.Add(item3);

        items2.Add(item4);
        items2.Add(item5);
        items2.Add(item6);

        var allItems = new List<CombMin>();
        allItems.Add(new CombMin { Combination = items1, MinCount = 104 });
        allItems.Add(new CombMin { Combination = items2, MinCount = 104 });

问题是:如何在不循环的情况下更新 allItems 中的字段 ItemCount(使用 Linq)？例如，如果 Index = 0，我想将 ItemCount 设置为 ItemCount-5。

Answer 1

基本解决方案:

allItems.ForEach(x => x.Combination.FirstOrDefault(ele => ele.Index == 0).ItemCount -= 5);

As mentioned in comment if there is only 1 element with index 1 then you can do is :

   allItems.ForEach(x => x.Combination.First(ele => ele.Index == 0).ItemCount -= 5);

If you are not sure that the given index exists in the collection you can do is

CombMin element = new CombMin();
int index = 25;//does not exists in the collection
element = allItems.FirstOrDefault(x => x.Combination.Any(ele => ele.Index == index));
if (element != null)
    element.Combination.FirstOrDefault(ele => ele.Index == index).ItemCount -= 5;