Linq和EF做单一条件查询和复合条件查询以及多表联合查询示例

单一条件查询：

vartable2Object = (fromt1indb.table1

join t2indb.table2 on t1.id equals t2.idselectt2).FirstOrDefault();

复合条件 查询：

多个主键 联合查询

vartable2Object = (fromt1indb.table1

join t2indb.table2

onnew{ t1.id, t1.another_id } equalsnew{ t2.id, t2.another_id }selectt2).FirstOrDefault();

多表联合查询：

Join3个Table

vartable2Object = (fromt1indb.table1

join t2indb.table2

onnew{ t1.id, t1.another_id } equalsnew{ t2.id, t2.another_id }

join t3indb.table3

onnew{ t2.id, t2.another_id } equalsnew{ t3.id, t3.another_id }selectt2).FirstOrDefault();