Entity Framework Tutorial Basics（34）：Table-Valued Function

Table-Valued Function in Entity Framework 5.0

Entity Framework 5.0 supports Table-valued functions of SQL Server.

Table-valued functions are similar to stored procedure with one key difference: the result of TVF is composable which means that it can be used in a LINQ query.

We have created a TVF GetCourseListByStudentID in the database that will return all the courses of a particular student. For example:

USE [SchoolDB]

    GO

    /****** Object:  UserDefinedFunction [dbo].[GetCourseListByStudentID]  */

    SET ANSI_NULLS ON

    GO

    SET QUOTED_IDENTIFIER ON

    GO

    CREATE FUNCTION [dbo].[GetCourseListByStudentID]

    (

        -- Add the parameters for the function here

        @studentID int

    )

    RETURNS TABLE

    AS

    RETURN

    (

        -- Add the SELECT statement with parameter references here

        select c.courseid, c.coursename,c.Location, c.TeacherId

    from student s left outer join studentcourse sc on sc.studentid = s.studentid left outer join course c on c.courseid = sc.courseid

    where s.studentid = @studentID

    )

Now, update your EDM and add this TVF into your EDM. Right click on the designer → select Update Model from the Database..

Expand Stored Procedures and Functions node → expand schema node (dbo schema in our case) → select 'GetCourseListByStudentID' and click Finish. Make sure that the checkbox for 'Import selected procedures and functions into the entity model' is checked (this will import the function automatically).

After you imported the function, you can verify it: Open Model Browser → expand Function Imports → right click on imported function 'GetCourseListByStudentID' → click Edit:

You can see that EDM has automatically created the complex type GetCourseListByStudentID_Result as a return collection type.

You can also select an existing entity as a return type if TVF returns the same columns as entity:

Now, you can use TVF with DBContext. For example:

using (var ctx = new SchoolDBEntities())

{

    //Execute TVF and filter result

    var courseList = ctx.GetCourseListByStudentID().Where(c => c.Location.SpatialEquals(DbGeography.FromText("POINT(-122.360 47.656)"))))

                            .ToList<GetCourseListByStudentID_Result>();

     foreach (GetCourseListByStudentID_Result cs in courseList)

                Console.WriteLine("Course Name: {0}, Course Location: {1}",

                            cs.CourseName, cs.Location);

}