C#中LINQ的简单用法示例

原创已于 2022-04-24 13:35:15 修改 · 361 阅读

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#C# #LINQ

于 2021-01-15 18:07:47 首次发布

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本文展示了如何使用C#的LINQ对集合进行分组和聚合操作，具体包括按指定字段分组、多值拼接及求和。示例中创建了一个JhInfo对象列表，然后通过GroupBy方法进行分组，Select方法处理分组后的数据，实现了按xmbh和htbh字段分组，将name字段值合并，并计算amount字段的总和。最后通过Find和FindAll方法进行了查找操作。

业务场景：

对集合分组，求和

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

namespace Test
{
    class Program
    {
        static void Main(string[] args)
        {
            JhInfo jh01 = new JhInfo() { xmbh = "xm01", htbh = "ht01", name = "甲", amount = 11 };
            JhInfo jh02 = new JhInfo() { xmbh = "xm01", htbh = "ht01", name = "乙", amount = 6 };
            JhInfo jh03 = new JhInfo() { xmbh = "xm01", htbh = "ht02", name = "丙", amount = 9 };

            List<JhInfo> list = new List<JhInfo>();
            list.Add(jh01);
            list.Add(jh02);
            list.Add(jh03);

            // 对集合 按 xmbh 和 htbh 分组，对name多值拼接，对amount求和
            List<JhInfo> aa = list.GroupBy(x => new { x.xmbh, x.htbh }).Select(y => new JhInfo{ 
                xmbh = y.Key.xmbh,
                htbh = y.Key.htbh,
                name = string.Join(",", y.Select(x => x.name).ToArray()),
                amount = y.Sum(x => x.amount)
            }).ToList();

            foreach (JhInfo a in aa)
            {
                Console.WriteLine("name：【" + a.name + "】Count: 【" + a.amount + "】");
            }
            

            // 从集合查找
            JhInfo findOne = list.Find(x => x.name.Equals("甲"));
            List<JhInfo> findAll = list.FindAll(x => x.xmbh.Equals("xm01"));
        }
    }


    class JhInfo
    {
        public string xmbh { get; set; }
        public string htbh { get; set; }
        public string name { get; set; }
        public int amount { get; set; }
    }
}