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  • LINQ 的一些相关基本语法

      类型 查询变量 = from 临时变量in 集合对象或数据库对象
                [where 条件表达式]
                [order by 条件]
                select 临时变量中被查询的值
                [group by 条件]

    1. 简单的查询

        var movies = from c in db.movies 

                 select c;   //此处是一个集合

        sql : select *  from db.movies 

      2. 带where 条件的查询

        movies = movies.Where(w =>w.ID>10); 

        sql :select * from  movies where ID>10

       3. 排序order by desc/asc
        var ss = from r in db.movies where r.ID > 10

    orderby r.ID descending //倒序 //

    orderby r.ID ascending //正序 select r; //正序

    var ss1 = db.movies .OrderBy(p => p.ID).Where(p => p.ID> 10).ToList(); //倒序

    var ss2 = db.movies .OrderByDescending(p => p.ID).Where(p => p.ID> 10).ToList();

    sql : select * from movies  where ID>10 order by ID desc; // or  asc 

    4.top

    //如果取最后一个可以按倒叙排列再取值
    var ss = (from r in db.movies  
    select r).FirstOrDefault();

    var ss1 = db.movies  .FirstOrDefault();
    //var ss1 = db.movies  .First();

     sql = select top(1) * from movies  ;

    5.包含,类似 like   

    var ss = from r in db.movies  
        where r.SortsText.Contains("张")
        select r;


    var aa= db.movies  .Where(p => p.Title.Contains("张")).ToList();
    sql = select * from movies  where Title like '%张%';

          6.连接查询

    var bb= from r in db.movies  
        join w in db.movies2  on r.VID equals w.MID
        orderby r.VID descending
    select r;


    var aa = db.movies  .Join(db.movies2 , p => p.VID , r => r.VID , (p, r) => p).OrderByDescending(p => p.VID ).ToList();
     sql = select r.* from movies   as r inner join dbo.movies2   as t on r.VID = t.MID order by r.VID desc;

          7.sql IN

    var aa= from p in db.movies
        where (new int?[] { 24, 25,26 }).Contains(p.VID )
        select p;
    foreach (var p in ss)
    {
    Response.Write(p.Sorts);
    }

    sql = select *  from movies    where VID in(24,25,26);

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  • 原文地址:https://www.cnblogs.com/condon/p/7080883.html
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