SQL Scope_Identity is returning 0 or -1

Question

I'm having issues getting the last row affected ID, it's returning 0, this means that it has an error on format being inserted. I executed the stored procedure and added the values manually, it return'd the correct ID. But when I try to do it with the code it keeps returning 0 or -1 ... I tried this last night after several hours and I'm already confused with the values it gave me.

C#:

conn.Open();

            cmd.Parameters.AddWithValue("@fileName", fileName);
            cmd.Parameters.AddWithValue("@filePrivacy", filePrivacy);

            cmd.Parameters.AddWithValue("@filePassword", filePassword);

            cmd.Parameters.AddWithValue("@fileDescription", fileDesc);
            cmd.Parameters.AddWithValue("@fileOwner", fileOwner);
            cmd.Parameters.AddWithValue("@fileDate", DateTime.Now);
            cmd.Parameters.AddWithValue("@fileExpire", DateTime.Now.AddMinutes(fileExpire));
            cmd.Parameters.AddWithValue("@fileCodeText", fileType);
            var fileID = cmd.Parameters.Add("@fileID", SqlDbType.Int);
            fileID.Direction = ParameterDirection.Output;

            int returnfileID = (int)cmd.ExecuteScalar();
            return returnfileID;

Stored Procedure:

CREATE PROCEDURE [dbo].[Upload]
@fileName nvarchar(20),
@filePrivacy int,
@filePassword nvarchar(50),
@fileDescription nvarchar(200),
@fileOwner nvarchar(14),
@fileDate smalldatetime,
@fileExpire smalldatetime,
@fileCodeText int,
@fileID int out

AS
INSERT INTO Files ([FileName], FilePrivacy, FilePassword, FileDescription, FileOwner, FileDate, FileExpire, FileCodeText)
VALUES (@fileName, @filePrivacy, @filePassword, @fileDescription, @fileOwner, @fileDate, @fileExpire, @fileCodeText)
SET @fileID = SCOPE_IDENTITY()
RETURN @fileID

SQL Table:

CREATE TABLE [dbo].[Files] (
[Id]              INT            IDENTITY (1, 1) NOT NULL,
[FileName]        NVARCHAR (20)  NOT NULL,
[FilePrivacy]     INT            NOT NULL,
[FilePassword]    NVARCHAR (50)  NULL,
[FileDescription] NVARCHAR (200) NULL,
[FileOwner]       NVARCHAR (14)  NOT NULL,
[FileDate]        SMALLDATETIME  NOT NULL,
[FileExpire]      SMALLDATETIME  NOT NULL,
[FileCodeText]    INT            NOT NULL,
PRIMARY KEY CLUSTERED ([Id] ASC)
);

Answer 1

ExecuteScalar 'Executes the query, and returns the first column of the first row in the result set returned by the query. Additional columns or rows are ignored'

If you select @fileID (instead of return) it should work.
Alternatively you could access the @fileID parameter value after you execute the query, in which case there's no real point having an ExecuteScalar, you could change it to to ExecutenonQuery.

Answer 2

Use in the SQL

SET @fileID= SCOPE_IDENTITY() RETURN @fileID

SELECT @@IDENTITY;

and in the C# code

 int returnfileID = Convert.ToInt32(cmdInsert.ExecuteScalar())

Answer 3

My initial thought is that you are getting back the stored procedure return code. @fileID should be returned by your stored procedure since you have set it as an OUTPUT parameter. Remove the RETURN from your stored procedure. It should pass back the output variable rather than the execution code that way.