根据类型组合列表中的元素并求和它们的值LINQ [英] Combine Elements in a List based on Type and Summate their Values, LINQ

问题描述

给出此结构.

我基本上希望能够获取具有多种类型的项目的列表，并创建一个新列表来精简每个相似类型的值之和.但是，这些类型的名称是动态的(它们可以有或没有特定的顺序，并且没有有限的列表)

I basically want to be able to take a list of items with multiple types, and create a new list that condenses down the sum of the values of each like-type. However the names of the types are dynamic (they may or may not have a specific order, and there is no finite list of them)

 using System.Linq;
using System.Collections.Generic;

class Item
{
    public ItemType Type;
    public int Value;

    public int Add(Item item)
    {
        return this.Value + item.Value;
    }
}

class ItemType
{
    public string Name;
}

class Test
{
    public static void Main()
    {
        List<ItemType> types = new List<ItemType>();
        types.Add(new ItemType { Name = "Type1" });
        types.Add(new ItemType { Name = "Type2" });
        types.Add(new ItemType { Name = "Type3" });

        List<Item> items = new List<Item>();

        for (int i = 0; i < 10; i++)
        {
            items.Add(new Item
            {
                Type = types.Single(t => t.Name == "Type1"),
                Value = 1
            });
        }

        for (int i = 0; i < 10; i++)
        {
            items.Add(new Item
            {
                Type = types.Single(t => t.Name == "Type2"),
                Value = 1
            });
        }

        for (int i = 0; i < 10; i++)
        {
            items.Add(new Item
            {
                Type = types.Single(t => t.Name == "Type3"),
                Value = 1
            });
        }

        List<Item> combined = new List<Item>();

        // create a list with 3 items, one of each 'type', with the sum of the total values of that type.
        // types included are not always known at runtime.
    }
}

推荐答案

类似的东西应该可以工作.警告:我没有编译它.

Something like this should work. Warning: I didn't compile this.

items.GroupBy(i => i.Name)
   .Select(g => new Item { Type= g.First().Name, Value = g.Sum(i => i.Value)})
   .ToList()

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