C#实战积累:常用的lambda表达式整理

int lamValue = 10;
Func<int,int> sum = x => x+lamValue;

public class AnonymousClass{
　　public int lamValue;
　　public AnonymousClass(int lamValue){
　　　　this.lamValue = lamValue;
　　}
　　public int AnonymousMethod(int x) => x+lamValue;
}

using System;

namespace Study
{
    [Serializable]
public class Goods
    {
/// <summary>
/// 商品名称
/// </summary>
public string Name { get; set; }
/// <summary>
/// 商品分类名称
/// </summary>
public string CategoryName { get; set; }
/// <summary>
/// 商品编码
/// </summary>
public string Code { get; set; }
/// <summary>
/// 商品单价
/// </summary>
public double Price { get; set; }
/// <summary>
/// 商品数量
/// </summary>
public int Count { get; set; }

    }
}

using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Linq;

namespace Study
{
class Program
    {
static void Main(string[] args)
        {
var list = new List<Goods>();
            list.Add(new Goods
            {
                Name = "小米12",
                CategoryName = "手机",
                Price = 3500.00,
                Code = "001",
                Count = 10
            });
            list.Add(new Goods
            {
                Name = "联想T50",
                CategoryName = "笔记本",
                Price = 8800.00,
                Code = "002",
                Count = 25
            });
            list.Add(new Goods
            {
                Name = "雷柏键鼠套装",
                CategoryName = "数码",
                Price = 688.00,
                Code = "003",
                Count = 60
            });
            list.Add(new Goods
            {
                Name = "华为蓝牙耳机",
                CategoryName = "数码",
                Price = 998.00,
                Code = "004",
                Count =7
            });
// 筛选分类是数码的数据
var list1 = list.Where(m => m.CategoryName == "数码").ToList();
// 筛选分类是数码或者手机的记录
var list2 = list.Where(m => m.CategoryName == "数码" || m.CategoryName=="手机").ToList();
// 按照价格升序排序
var list3 = list.OrderBy(m => m.Price).ToList();
// 按照价格降序
var list4 = list.OrderByDescending(m => m.Price).ToList();
// 按照分类进行分组只展示分类名称
var list5 = list.GroupBy(m => m.CategoryName).ToList();
// 查询分类是数码的商品的总数量
var list6 = list.Where(m=>m.CategoryName=="数码").Sum(m => m.Count);
// 查询商品名称包含机这个关键字的平均价格
var list7 = list.Where(m => m.Name.Contains("机")).Average(m => m.Price);
// 根据分类进行分组 获取分类名、总数量、平均单价
var list8 = list.GroupBy(m => m.CategoryName).Select(n => new Goods
            {
                CategoryName=n.FirstOrDefault().CategoryName,
                Price=n.Average(s=>s.Price),
                Count = n.Sum(s => s.Count)
            });
// 获取当前列表的前两行记录
var list9 = list.Take(2).ToList();
// 获取后两行数据
var list10 = list.TakeLast(2).ToList();
// 针对列表内存形式的分页 跳过第一条记录，往后查询两条
var list11 = list.Skip(1).Take(2).ToList();

// 针对整个列表所有属性比对去重
var list12 = list.Distinct().ToList();
// 根据分类名称去重
var list13 = list.Select(m => m.CategoryName).Distinct().ToList();
// 逗号拼接字符串 针对数值类型字段的拼接 获取前端字符串展示
var json1 = string.Join(',', list.Select(m => m.Code));
// 逗号加'' 单引号拼接字符串主要是用来数据库字段不为数值类型的 in 查询sql拼接
var json2 = string.Join("','", list.Select(m => m.Name));
            Console.WriteLine(json1);
            Console.WriteLine("逆序之前");
            foreach (var item in list)
            {
                Console.WriteLine(JsonConvert.SerializeObject(item));
            }
// list 逆序操作
            list.Reverse();
            Console.WriteLine("逆序之后");
            foreach (var item in list)
            {                Console.WriteLine(JsonConvert.SerializeObject(item));
            }           

            Console.WriteLine("Hello World!");
        }
    }
}