EntityFramework - Functions

介绍:

Function 类一般用于 在 EF 查询过程中对 EF 本身不支持的查询方式的一个扩展.

比如在 EF Linq 中不支持 Date 数据类型的比较查询.

在 Function 中则提供了更好的支持

 

使用方法:

直接在 lambda 表达式中使用 Function 方法.

例如:

query = query.Where(d => DbFunctions.DiffDays(d.发布时间, DateTime.Now) == 0);

 

类别分类:

在不同的 命名空间下有针对不同的查询方式做的扩展

System.Data.Objects.SqlClient.SqlFunctions

Provides common language runtime (CLR) methods that call functions in the database in LINQ to Entities queries.

System.Data.Entity.SqlServer.SqlFunctions

Contains function stubs that expose SqlServer methods in Linq to Entities.

System.Data.Objects.EntityFunctions

Provides common language runtime (CLR) methods that expose conceptual model canonical functions in LINQ to Entities queries. For information about canonical functions, see Canonical Functions.

System.Data.EntityCore.Objects.EntityFunctions

Provides common language runtime (CLR) methods that expose EDM canonical functions for use in DbContext or ObjectContext LINQ to Entities queries.

System.Data.Entity.DbFunctions

Provides common language runtime (CLR) methods that expose EDM canonical functions for use in DbContext or ObjectContext LINQ to Entities queries.