Question

假设我有一个像这样的数据库记录列表：

Warehouse   goods

A           apple

A           orange

B           apple

B           banana

是否可以使用linq选择两个对象，说对象A和对象B每个都包含其商品的集合？

Answer 1

Linq更多的是查询，而不是你对查询结果的处理方式。这就是为什么您会看到Select和Where但不是Add或Update等方法的原因。

您可以获取查询的结果并将它们添加到两个单独的集合中，或者您可以迭代集合中的项目并对它们执行多个操作，例如检查它们并将它们添加到一个或多个集合中。 / p>

Answer 2

你可以这样做：

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

namespace SO36322037
{
    class Record
    {
        public string Warehouse { get; set; }
        public string Goods { get; set; }
    }

    class Program
    {

        static void Main()
        {
            var list = new List<Record>
            {
                new Record {Warehouse = "A", Goods = "apple"},
                new Record {Warehouse = "A", Goods = "orange"},
                new Record {Warehouse = "B", Goods = "apple"},
                new Record {Warehouse = "B", Goods = "banana"},
            };

            var result = list.GroupBy(l => l.Warehouse, l => l.Goods).ToList();
            foreach (var warehouse in result)
            {
                Console.WriteLine($"Warehouse: {warehouse.Key}");
                foreach (var goods in warehouse)
                {
                    Console.WriteLine($"\tGoods: {goods}");
                }
            }

            // This is your object A
            var A = result.Single(x => x.Key == "A").ToList();

            // This is your object B
            var B = result.Single(x => x.Key == "B").ToList();

        }
    }
}

Answer 3

如果我理解正确，你可以使用'group by'

做类似的事情

var items = new List<Record>
        {
            new Record {Warehouse = "A", Goods = "apple"},
            new Record {Warehouse = "A", Goods = "orange"},
            new Record {Warehouse = "B", Goods = "apple"},
            new Record {Warehouse = "B", Goods = "banana"},
        };
var warehouses = from item in items
                 group item.Goods by item.Warehouse

你可以像这样迭代结果

foreach(var warehouse in warehouses){
    //...
    foreach(var item in warehouse){
         //...
    }
}

Linq选择包含集合类型变量的对象

3 个答案: