场景:在实际的项目中使用EntityFramework都会遇到使用Ef处理连接查询的问题,这里做一些小例子如何通过Linq语法处理内连接(inner join)、外连接(left/right outer join); 废话不多说先看实体类: 1.内连接: Linq: varquery =fromstincontext.SchoolBoysjoinglincontext.SchoolGirlsonst.GirlfriendIdequalsgl.Idselectnew{...
foreach (var item in query) { Console.WriteLine("{0} {1} {2}", item.ClassID, item.ClassName, item.Student.Name); } } } Console.ReadLine(); } Outer join时必须将join后的表into到一个新的变量gc中,然后要用gc.DefaultIfEmpty()表示外连接。 linq to sql相关随笔: 1. 从CUD开始,如何使用L...
LINQ有两个联接操作符:Join和GroupJoin。 1. Join Join操作符类似于T-SQL中的inner join,它将两个数据源相联接,根据两个数据源中相等的值进行匹配。例如,可以将产品表与产品类别表相联接,得到产品名称和与其相对应的类别名称。以下的代码演示了这一点: //查询语法 var query = (from p in db.Products join...
特别简单,就不贴sql了,继续看outer join: staticvoidMain(string[] args) {using(varwriter =newStreamWriter(WatchSqlPath,false, Encoding.UTF8)) {using(DbAppDataContext db =newDbAppDataContext()) { db.Log=writer;//left outer joinvarquery =fromsindb.Students join cindb.Classes on s.ClassID eq...
varleftOuterJoinQuery=fromleftindb.LeftTablejoinrightindb.RightTableonleft.Key equals right.KeyintojoinDatafromrightinjoinData.DefaultIfEmpty()selectnew{LeftKey=left.Key,RightData=right}; 在这个示例中,我们使用join关键字将左表和右表进行连接,并使用into关键字将连接结果存储在joinData变量中。然后,我们使...
join sinsalaryList on u.id equals s.user_id select s;/*C#写法2 <Lambda写法>*/IEnumerable<Salary>SalaryList=list.Join(inner:salaryList,/*inner: 可以省略*/outerKeySelector:u=>u.id,/*outerKeySelector: 可以省略*/innerKeySelector:s=>s.user_id,/*innerKeySelector: 可以省略*/resultSelector...
GroupJoin arguments Query syntax fromouter-varinouter-enumerablejoininner-varininner-enumerableonouter-key-exprequalsinner-key-expr[ into identifier ] Overview Join 和 GroupJoin 将两个输入序列网格化为一个输出序列。 Join 发出平坦的输出; GroupJoin 发出分层输出。
同样,Linq的join方法也有两种写法: 代码语言:dotnet 复制 /* C#写法1 <Linq写法>*/IEnumerable<Salary>SalaryList=fromuinlistjoinsinsalaryListonu.id equals s.user_idselects;/*C#写法2 <Lambda写法>*/IEnumerable<Salary>SalaryList=list.Join(inner:salaryList,/*inner: 可以省略*/outerKeySelector:u=>u....
can I query a struct (or class) to get a list of it's attributes and data types? Can I sell a game made using Visual Studio 2015 COMMUNITY Can i specify which sql index to use, in Linq - querry? Can I trigger timer interval of 24 hours? Can I use a javascript function in...
can I query a struct (or class) to get a list of it's attributes and data types? Can I sell a game made using Visual Studio 2015 COMMUNITY Can i specify which sql index to use, in Linq - querry? Can I trigger timer interval of 24 hours? Can I use a javascript function in ...