Question

我想从带有列表的表中选择许多值。我有FabricTable（年份是int）：

+----+-------+---------+------+
| Id | Color | Texture | Year |
+----+-------+---------+------+
| 1  | Red   | Rough   | 2019 |
+----+-------+---------+------+
| 2  | Green | Soft    | 2019 |
+----+-------+---------+------+
| 3  | Blue  | Rough   | 2019 |
+----+-------+---------+------+
| 4  | Red   | Med     | 2019 |
+----+-------+---------+------+
| 5  | Blue  | Soft    | 2018 |
+----+-------+---------+------+

我有selectedItems个列表（年份为int）：

+---------+------+
| Texture | Year |
+---------+------+
| Rough   | 2019 |
+---------+------+
| Soft    | 2019 |
+---------+------+

我想从表中获取Id，其结果应为Id = 1，2和3。

如何在C＃中使用Linq实现此目的？我只需要按Texture和Year

进行选择

这是我尝试过的方法，但是我不确定如何从具有多个值的列表中进行选择（selectedItems是一个列表，但我不知道如何查询多个列）：

db.FabricTable.Select(o => o.Texture == selectedItems.Texture && o.Year == selectItems.Year)

Answer 1

使用selectedItems.Texture时会出现编译器错误，因为selectedItem是一个包含具有Texture属性的对象的列表。在FabricTable中搜索所需项目时，您需要检查列表中的所有项目：

var items = db.FabricTable.Where(o => selectedItems.Any(selectedItem => o.Texture == selectedItem.Texture && o.Year == selectedItem.Year));

Answer 2

尝试以下操作：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;


namespace ConsoleApplication120
{
    class Program
    {
        static void Main(string[] args)
        {
            List<Item> items = new List<Item>() { 
                new Item() { Id = 1, Color = "Red", Texture = "Rough",  Year = 2019},
                new Item() { Id = 2, Color = "Green", Texture = "Soft",  Year = 2019},
                new Item() { Id = 3, Color = "Blue", Texture = "Rough",  Year = 2019},
                new Item() { Id = 4, Color = "Red", Texture = "Soft",  Year = 2018}
            };
            DataTable dt = new DataTable();
            dt.Columns.Add("Color", typeof(string));
            dt.Columns.Add("Texture", typeof(string));
            dt.Columns.Add("Year", typeof(int));

            foreach (Item item in items.Where(x => (x.Texture == "Rough") && (x.Year == 2019)))
            {
                dt.Rows.Add(new object[] { item.Color, item.Texture, item.Year });
            }

        }

    }
    public class Item
    {
        public int Id { get; set; }
        public string Color { get; set; }
        public string Texture { get; set; }
        public int Year { get; set; }
    }

}

C＃LINQ从具有多个字段的列表中选择表

2 个答案: