[VS 2010 + VB.Net] How to call a module into another module

Question

Hi,

I have a VB.Net interface that communicates with an Access 2k3 Database using this module:

Module MOD_ENGINE
    'Declare Database connections controls
    Dim con As New OleDb.OleDbConnection
    Dim dbProvider, dbSource As String
    Dim AccessCommand As OleDb.OleDbCommand
    'Connect to Access Database and activate the Engine
    Public Sub EngineConnect()
        dbProvider = "Provider=Microsoft.Jet.OLEDB.4.0;"
        dbSource = "..................................;"
        con.ConnectionString = dbProvider & dbSource
    End Sub
End Module

and another module that has queries procedures:

    'Populate ComboBox
    Public Sub popCboBox()
        sql = "........." 
        da = New OleDb.OleDbDataAdapter(sql, con)
        da.Fill(ds, "Tab")
        form.CboBox.DataSource = ds.Tables(0)
        form.CboBox.DisplayMember = "Data1"
        form.CboBox.ValueMember = "Data1"
    End Sub

I want to call EngineConnect procedure from MOD_ENGINE module into popCboBox module so I can ignate the engine!

How can I do it, please?

Regards

Answer 1

While generally global module objects are not a good idea, the reason you can't access your 'con' connection object from MOD_ENGINE in your other module is because you used DIM to declare them. DIM is the equivalent of declaring them private. If you were to change Dim to Friend or Public, you would be able to call your con variable from the module. If you really want to do it this way, how about making the connection object more of a singleton?

Something along these lines:

Module MOD_ENGINE
    'Declare Database connections controls
    Dim con As OleDb.OleDbConnection = Nothing

    Public Function GetConnection() As OleDb.OleDbConnection

        Try
            If con Is Nothing Then
                con = New OleDb.OleDbConnection("CONNECTION STRING HERE")
            End If
            If con.State <> ConnectionState.Open Then
                con.Open()
            End If
            Return con
        Catch ex As Exception
            'HANDLE ERROR
            Return Nothing
        End Try

    End Function
End Module
Module OtherModule

    Public Sub DoDatabaseStuff()
        Dim myCon As OleDb.OleDbConnection = MOD_ENGINE.GetConnection

        If myCon IsNot Nothing Then
            'WE HAVE A VALID OPEN CONNECTION TO DB
        Else
            'ERROR OCCURED IN GetConnection ROUTINE
        End If

    End Sub

End Module

---

Matt Kleinwaks - MSMVP MSDN Forums Moderator - www.zerosandtheone.com

Answer 2

Hi Admin-Dev,

Do you have any update?

Best regards,

---

Mike Feng
MSDN Community Support | Feedback to us
Please remember to mark the replies as answers if they help and unmark them if they provide no help.

Answer 3

Hi Mike,

I tried many alternatives solutions, sidewalk solution... but kleinma answer is the final

Thanks