Attach MDF file to client computer

[Alexandru_mbm]

I have an app that uses an SQL Server Express 2008, .mdf file.

On my computer where i've coded the app all work's fine using this code:

        If conexiune.State <> ConnectionState.Open Then

            Try

                conexiune.ConnectionString = "Data Source=.\SQLEXPRESS; AttachDbFilename=" & My.Settings.locatie_baza_date.ToString & "; Initial Catalog=" & My.Settings.locatie_baza_date.ToString & "; Integrated Security=True; Connect Timeout=30; User Instance=True;"
                conexiune.Open()

            Catch ex As Exception

                frm_afisare_eroare.lbl_cod_eroare.Text = Err.Number
                frm_afisare_eroare.txt_detalii_eroare.Text = ex.Message & vbCrLf & vbCrLf & ex.StackTrace & vbCrLf & vbCrLf & " (" & Err.Source & "-" & Err.LastDllError & "-" & Err.Erl & ")"
                frm_afisare_eroare.Show()

            End Try

        Else
        End If

On the clients computer i've installed the SQL Server Express 2008 and the application and i got this error:

ExecuteScalar requires an open avalaible Connection.

What's wrong in this code?