Problem returning value from stored procedure

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I have a problem getting a returned value from a stored procedure, it's just returning dbnull, I checked the SP and that's working okay

Stored Procedure :-

SQL

alter PROCEDURE UPDATE_SiteVisitors2
	
@VPCode nvarchar(10),


AS

BEGIN

declare @Exists INT 

SET NOCOUNT ON;

IF EXISTS (select vpcode FROM SiteVisitors WHERE vpcode=@vpcode)

BEGIN

update sitevisitors

set

VSignOut = getdate()

where VPCode=@VPCode

		SET @Exists = 1

END

ELSE

BEGIN

		SET @Exists = 0
END

RETURN @Exists

END

VB :-

VB

<pre>    Public Function updateVisitors(ByVal VPCode As String)

        Dim conn As New System.Data.SqlClient.SqlConnection(access.SQLstrconn)
        Dim sql As String = "UPDATE_SiteVisitors2 '" & VPCode & "'"
        Dim Cmd As New System.Data.SqlClient.SqlCommand(sql, conn)
        Dim Par As New System.Data.SqlClient.SqlParameter
        Cmd.Parameters.Add("@Exists", SqlDbType.Int)
        Cmd.Parameters("@Exists").Direction = ParameterDirection.Output

        conn.Open()
        Cmd.ExecuteNonQuery()

        SignIn.exists = Cmd.Parameters("@Exists").Value

        conn.Close()

'signin.exists is a public variable int

        MsgBox(SignIn.exists)

        Return SignIn.exists

    End Function

What I have tried:

Tried a few things but just getting DBNULL

Posted 5-May-17 3:13am

caffrey_1

Updated 5-May-17 3:55am

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Comments

CHill60 5-May-17 9:21am

Is VSignOut actually being updated?

caffrey_1 5-May-17 9:32am

Yes it is, the update works fine just @Exists is just returned as DBNULL

[no name] 5-May-17 9:27am

cmd.CommandType = CommandType.StoredProcedure

caffrey_1 5-May-17 9:34am

Throws a couldn't find stored procedure exception ?

[no name] 5-May-17 9:40am

That is because the name of your SP is UPDATE_SiteVisitors2 not UPDATE_SiteVisitors2 + someVPCode.

caffrey_1 5-May-17 10:06am

Yep, this really helped thanks

3 solutions

Solution 2

@Exists is not an output parameter, it's a return value
Try the following:

VB

Dim sql As String = "UPDATE_SiteVisitors2"
        Dim Cmd As New System.Data.SqlClient.SqlCommand(sql, conn)
        Cmd.Parameters.Add("@Exists", SqlDbType.Int)
        Cmd.Parameters("@Exists").Direction = ParameterDirection.ReturnValue
        Dim par As SqlParameter = Cmd.Parameters.Add("@VP", SqlDbType.NVarChar)
        par.Direction = ParameterDirection.Input
        par.Value = VPCode
...

Posted 5-May-17 3:34am

CHill60

Solution 1

You need to declare your variable in SQL as OUTPUT. A good example is here, Returning Data by Using OUTPUT Parameters[^].

My preference is to NOT use output parameters. Instead of RETURN in your SQL just do SELECT @Exists AS Exists

Then in C#

C#

String returnValue;
Object temp = cmd.ExecuteScalar();
if (temp!= null){
  returnValue = temp.ToString();
}

Either way you go is fine as long as you do it right. ;)

Posted 5-May-17 3:26am

ZurdoDev

Updated 5-May-17 3:27am

v2

Comments

caffrey_1 5-May-17 9:36am

I was considering doing it an alternative way and fill a dataset, if the dataset has no rows etc. Just trying to do it a neater way!

ZurdoDev 5-May-17 9:40am

Since you just return one value it is my understanding that ExecuteScalar() is more efficient than an output parameter.

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caffrey_1 · Accepted Answer · 2017-05-05T03:55:00

Nailed it. was thanks to the

Cmd.CommandType = CommandType.StoredProcedure

pointer

Thanks for the help and pointers much appreciated

New code

VB

Public Function updateVisitors(ByVal VPCode As String)



       Dim conn As New System.Data.SqlClient.SqlConnection(access.SQLstrconn)


       'Dim sql As String = "UPDATE_SiteVisitors2 '" & VPCode & "'"
       Dim sql As String = "UPDATE_SiteVisitors2"
       Dim Cmd As New System.Data.SqlClient.SqlCommand(sql, conn)
       Cmd.CommandType = CommandType.StoredProcedure
       Cmd.Parameters.Add("@VPCode", SqlDbType.VarChar, 10, ParameterDirection.Input).Value = VPCode
       Cmd.Parameters.Add("@Exists", SqlDbType.Int)
       Cmd.Parameters("@Exists").Direction = ParameterDirection.Output
       conn.Open()

       Cmd.ExecuteNonQuery()

       SignIn.exists = Cmd.Parameters("@Exists").Value

       conn.Close()


       MsgBox(SignIn.exists)

       Return SignIn.exists

   End Function

SQL slightly changed

SQL

alter PROCEDURE UPDATE_SiteVisitors2
	
@VPCode nvarchar(10),
@Exists INT OUTPUT

AS

BEGIN

SET NOCOUNT ON;

--declare @Exists INT 

IF EXISTS (select vpcode FROM SiteVisitors WHERE vpcode=@vpcode)


BEGIN

update sitevisitors

set

VSignOut = getdate()

where VPCode=@VPCode


		set @Exists = 1
END
ELSE
BEGIN
		set @Exists = 0
END

RETURN @Exists
END