实体框架 - 存储过程返回值

Question

I am trying to get the return value of a stored procedure. Here is an example of such a stored procedure:

select
    Name,
    IsEnabled
from
    dbo.something
where
    ID = @ID

if @@rowcount = 0
    return 1    

return

This is a simple select. If 0 rows are found, my result set will be null, but I will still have a return value.

This is a bad example, as this is a select, so sure I could find if 0 rows were returned. However, on an Insert, delete, or other calls, we need this return value to know if there was a problem. I have been unable to find a way to get this return value. I can get output values, I can get result sets, but no return value.

I can get the return value if I call SQL manually, or even if I run a SqlCommand using the Entity Framework, but this is not what I want to do.

Has anyone ever been able to get the return value from a stored procedure using Entity Framework?

Thanks for the help!

Answer 1

I guess support of stored procedure return values depends on version of Entity framework. Although directly returning value didn't work for me I managed to get value using OUTPUT stored procedure parameter. Example:

USE [YOUR_DB_NAME]
GO

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

CREATE PROCEDURE [dbo].[TestReturnValue]
    @InputValue int = 0,
    @Result int OUTPUT
AS
BEGIN
    SET NOCOUNT ON;
    SELECT @Result  = @InputValue
    RETURN(@InputValue);
END

This is test code:

void TestReturnValue()
{
    using (var db = new YourDBContext())
    {
        var result = new System.Data.Objects.ObjectParameter("Result", 0);
        Console.WriteLine("SP returned {0}", db.TestReturnValue(123, result));
        Console.WriteLine("Output param {0}", result.Value);
    }
}

And this is output:

SP returned -1
Output param 123

As you see directly returned value output some rubbish but OUTPUT parameters works!

This article provides general info on two ways of returning values from SP

Hope this helps

Answer 2

I have been able to get the return value (and also output and input parameters) with Entity Framework 5 (but I think it works from version 4.x) using the code first approach. From your post I don't see what version of EF you are using and how you're doing your mapping; if you consider to use code-first approach here you can find my post with the solution:

Get return value from stored procedure

Answer 3

No. Entity Framework doesn't have rich stored procedure support because its an ORM, not a SQL replacement.

As you have already discovered, if you need to use less common (more advanced?) features of stored procedures, you'll have to use good old fashioned ADO.NET.

Answer 4

You must use the "Context.Database.SqlQuery",and specify the output type of the stored procedure

        var spReturnVaue = Context.Database.SqlQuery<Type>("[schema].YourSp").FirstOrDefault();

        int firstId = Context.Database.SqlQuery<int>("[dbo].GetFirstId").FirstOrDefault();

Answer 5

In order to get the interested result in EF, you should return a same structure (not 1 and Name, IsEnabled) In this query you should return '',0 for example instead of 1 in the if condition:

select
    Name,
    IsEnabled
from
    dbo.something
where
    ID = @ID

if @@rowcount = 0
    return '',0