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var q = from c in db.Customers where c.City == "London" select c 等价于SQL语句 select * from db.Customers c where c.City = "London" 然后把记录集赋给变量q foreach (var v in q) 表示记录集q里的每一条记录v要执行下马{}里的操作

System.Linq 命名空间提供支持使用语言集成查询 (LINQ) 进行查询的类和接口 using + 命名空间名字,这样可以在程序中直接用命名空间中的类型,而不必指定类型的详细命名空间.

LINQ 按多个字段排序(orderby、thenby、Take) orderby 子句解析为 OrderBy()方法,orderby descending 子句解析为OrderBy Descending()方法: var racers = Formula1.GetChampions(). Where(r = > r.Country == "Brazil"). OrderByDescending(...

在写LINQ语句的时候,往往会看到.AsEnumerable() 和 .AsQueryable() 。 例如: [csharp] view plaincopy string strcon = "Data Source=.\\SQLEXPRESS;Initial Catalog=Db_Example;Persist Security Info=True;User ID=sa;Password=sa"; SqlConn...

命名空间“System”中不存在类型或命名空间名称“Linq”(是缺少程序集引用吗?) Visual Studio 2008中当建立新文件时,遇到这样的问题: “using System.Linq命名空间无法引用!!1 解决方法:在解决方案上点击右键–添加引用–浏览—找到Microsoft.Net-...

假设你上图表格数据为 DataTable dt,列分别为AA,BB,CC,DD var query = from p in dt.AsEnumerable() //分组 group p by new { t1 = p.Field("AA").ToString().Substring(0, p.Field("AA").ToString().Length - 2), t2 = p.Field("BB"), t3 = p....

SQL:select * from A,B where A.cpID=B.cpID and A.cbID=B.cbID LINQ:var p = from t1 in a from t2 in b from t3 in c where t1.cpid equal t2.cpid and t1.cbid equal t3.cbid select new { t1, t2.cpid }

string[] ids = (from DeductionBill in t_ds_DeductionBill where t_ds_DeductionBill .BillNumber.Equals(c.BillNumber)) .ToArray(); TotalWeight= (from Order in t_kd_Order where(item => ids.Contains(item.OrderID)) select Order.Total...

var value=(from v in db.tbl select v.name).Distinct().ToList();

SQL:select * from A,B where A.cpID=B.cpID and A.cbID=B.cbID LINQ:var p = from t1 in a from t2 in b from t3 in c where t1.cpid equal t2.cpid and t1.cbid equal t3.cbid select new { t1, t2.cpid } linq 也能实现 sum、groupby 的效果...

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