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

2019-11-14 15:45:13

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单一条件查询：

var table2Object = (from t1 in db.table1             join t2 in db.table2 on t1.id equals t2.id                      select t2).FirstOrDefault();

复合条件查询：

多个主键联合查询

var table2Object = (from t1 in db.table1             join t2 in db.table2             on new { t1.id, t1.another_id } equals new { t2.id, t2.another_id }             select t2).FirstOrDefault();

多表联合查询：

Join3个Table

var table2Object = (from t1 in db.table1             join t2 in db.table2             on new { t1.id, t1.another_id } equals new { t2.id, t2.another_id }             join t3 in db.table3             on new { t2.id, t2.another_id } equals new { t3.id, t3.another_id }             select t2).FirstOrDefault();