Entity Framework Core 3.1 学习笔记6 查询

using Demo.Data;
using Demo.Domain;
using Microsoft.EntityFrameworkCore;
using System;
using System.Linq;

namespace Demo.App
{
    class Program
    {
        static void Main(string[] args)
        {
            using var context = new DemoContext();
            //var italy = "Italy";
            //var leagues = context.Leagues
            //    .Where(x=>x.Country== italy)//变量参数化查询,直接用值就不是
            //    .ToList();
            ////var leagues2 = (from lg in context.Leagues where lg.Country== "Italy" select lg).ToList();
            //foreach (var league in leagues)//context.Leagues
            //{
            //    Console.WriteLine(league.Name);
            //}

            //var leagues = context.Leagues
            //    .Where(x => x.Country.Contains("e"))// 输出 [Country] CHARINDEX(N'e', [l].[Country]) > 0
            //    .ToList();
            ////var leagues2 = (from lg in context.Leagues where lg.Country== "Italy" select lg).ToList();
            //foreach (var league in leagues)//context.Leagues
            //{
            //    Console.WriteLine(league.Name);
            //}

            var leagues = context.Leagues
           .Where(x => EF.Functions.Like(x.Country,"%e%"))//  输出[Country] LIKE N'%e%'
           .ToList();
            //var leagues2 = (from lg in context.Leagues where lg.Country== "Italy" select lg).ToList();
            foreach (var league in leagues)//context.Leagues
            {
                Console.WriteLine(league.Name);
            }


            //ToList()
            //First() 第一个,没有会报错
            //FirstOrDefault 第一个，没有返回默认值
            //Single SingleOrDefault Last() LastOrDefault() 一个 最后一个必须排序，否则报错
            //Count() LongCount() Min() Max() Average() Sum() 总数  Long类型总数 最大 平均 求和
            //Find 寻找

            //异步版本
            //ToListAsync()
            //...


            Console.ReadKey();
        }
    }
}