Return Value from SQL Stored Procedure - sql-server

Question

I have a stored procedure in a Microsoft SQL Server database:
USE [ProjectIndexer]
GO
/****** Object: StoredProcedure [files].[add_file] Script Date: 12/12/2014 1:34:20 PM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE [files].[add_file]
#FILENAME varchar(255),
#EXTENSION nvarchar(8),
#PATH_FULL varchar(255),
#RELATIVE_PATH varchar(255),
#JOB varchar(15),
#DATE_MODIFIED datetimeoffset(7),
#SIZE BIGINT,
#INDEX_MODULE INT,
#FILE_TYPE varchar(255),
#DOC_TYPE varchar(255),
#DISCIPLINE varchar(255)
AS
DECLARE #file_id sql_variant
--Insert values for new file
INSERT INTO files.GENERAL
(FILENAME, EXTENSION, PATH_FULL, RELATIVE_PATH, JOB, DATE_MODIFIED, SIZE, INDEX_MODULE, FILE_TYPE, DOC_TYPE, DISCIPLINE)
VALUES(#FILENAME, #EXTENSION, #PATH_FULL, #RELATIVE_PATH, #JOB, #DATE_MODIFIED, #SIZE, #INDEX_MODULE, #FILE_TYPE, #DOC_TYPE, #DISCIPLINE);
--Get the ID of this new file
SELECT #file_id = current_value FROM sys.sequences WHERE name = 'FILE_ID_SEQ';
--Return ID
RETURN CONVERT(bigint, #file_id)
I am trying to run this procedure in a VB application developed in Visual Studio 2012, using table adapters:
Dim myFilesGeneralTableAdapter As New FILES_GeneralTableAdapter
Dim FileID As Int32
FileID = myFilesGeneralTableAdapter.AddFile(FileName, fileExtension, foundFile, fileRelativePath, JobNumber, fileDateModified, fileSize, Nothing, Nothing, Nothing, Nothing)
For some reason, the function isn't returning the value to the VB variable 'FileID'. I can, however, use the "Preview Data" feature in the dataset designer to insert values for the above parameters in Visual Studio, and in that environment I'm able to get a returned value.
This suggests to me that my syntax in my VB module is wrong. Can anyone tell me what the error is?

Answer 1

Have you considered using System.Data.SqlClient.SqlCommand? You can use it to call your stored procedure, add the parameter values, and execute it in such a way that you retrieve a single value, i.e.
Try
'Create command'
Dim command As New SqlCommand
command.CommandType = CommandType.StoredProcedure
conn = New SqlConnection(myConnString)
command.Connection = conn
command.CommandText = "add_file"
command.Parameters.AddWithValue("#Filename", [Filename])
...
command.Parameters.AddWithValue("#Discipline", Discipline)
command.Connection.Open()
Dim i As Int64 = command.ExecuteScalar()
command.Connection.Close()
'returns record ID'
Return i
Catch ex As Exception
Throw ex
Finally
If conn.State <> ConnectionState.Closed Then
conn.Close()
End If
End Try
Please note that, in this example, "myConnString" is a String with the value of my connection string for the database I'm connecting to.

Answer 2

I took the good advice of transitioning the script to an Entity Framework model. At first, the stored procedure did not return what I wanted (it only returned an integer value of 1), but I found a resource online that instructed me to create a "Function Import" in the EF model. After doing that and properly matching variable types I managed to get the stored procedure to return the right value in Visual Studio. Here's a good resoure:
http://www.devtoolshed.com/using-stored-procedures-entity-framework-scalar-return-values

Answer 3

Outside of converting from TableAdapter to Entity Framework (a good move regardless), you would be much_better off returning such a value as either an OUTPUT parameter or in a result set. A stored procedure return value is really intended to convey a status code of the operation and is hence pretty limited.
Also, by doing the following operation after the INSERT (i.e. as a separate step),
--Get the ID of this new file
SELECT #file_id = current_value FROM sys.sequences WHERE name = 'FILE_ID_SEQ';
you are risking getting an incorrect value if some other process inserts into that table at roughly the same time (i.e. between this particular INSERT and this particular SELECT).
Given both of the above issues, it would be fairly simple, and very reliable, to instead use the OUTPUT clause on the INSERT statement:
--Insert values for new file
INSERT INTO files.GENERAL
(FILENAME, EXTENSION, PATH_FULL, RELATIVE_PATH, JOB, DATE_MODIFIED, SIZE,
INDEX_MODULE, FILE_TYPE, DOC_TYPE, DISCIPLINE)
OUTPUT INSERTED.FILE_ID
VALUES(#FILENAME, #EXTENSION, #PATH_FULL, #RELATIVE_PATH, #JOB, #DATE_MODIFIED,
#SIZE, #INDEX_MODULE, #FILE_TYPE, #DOC_TYPE, #DISCIPLINE);
That will generate a 1 row, 1 column result set. The column will be named FILE_ID or whatever the actual field name is (I guess based on the naming convention used for the other fields and the variable).
Then get rid of the DECLARE #file_id, the SELECT ..., and the RETURN ....