Visual Basic

 Public Sub uchenici_DataU()
        
        If Exists(strAcessFilePath11 & "\Update.mdb") Or Exists(strAcessFilePath11 & "\Update.accdb") Then

            Dim selectdata2 As String
            selectdata2 = "SELECT Students.[ID number], Students.[Name 1], Students.[Name 2], Students.[Name 3], [Code Class].[Class No], [Code Paralell class].[Paralell class Name], Students.Address FROM (([C<ode Paralell class] INNER JOIN [Code Class] ON [Code Paralell class].[Paralell class ID] = [Code Class].[Paralell class]) INNER JOIN [Class Details] ON [Code Class].[Class ID] = [Class Details].Class) INNER JOIN (Students INNER JOIN StudentClass ON Students.[ID number] = StudentClass.[ID number]) ON ([Class Details].BasicClass = StudentClass.BasicClass) AND ([Class Details].Group = StudentClass.Group) AND ([Class Details].Class = StudentClass.Class) WHERE (((StudentClass.[Position])=1)) ORDER BY [Code Class].[Class No], [Code Paralell class].[Paralell class Name]"
            Dim strConn As String
            Dim reader1 As OleDbDataReader
            strConn = "Provider=Microsoft.Jet.OLEDB.4.0; Data Source=" & strAcessFilePath3 & ";User ID=Admin;Password="
            Using theConnection As New OleDbConnection(con_str)
                theConnection.Open()
                Using OleDbCommand2 = New OleDbCommand(selectdata2, theConnection)
                    reader1 = OleDbCommand2.ExecuteReader()
                    FlowLayoutPanel1.Visible = True
                    ProgressBar1.MarqueeAnimationSpeed = 50
                    ProgressBar1.Style = ProgressBarStyle.Marquee
                    While (reader1.Read())
                        masiv(0) = reader1.Item(0)
                        If masiv(0).Length = 8 Then
                            masiv(0) = "00" & masiv(0)
                        ElseIf masiv(0).Length = 9 Then
                            masiv(0) = "0" & masiv(0)
                        End If
                        masiv(1) = reader1.Item(1).ToString & " " & reader1.Item(2).ToString & " " & reader1.Item(3).ToString
                        masiv(2) = reader1.Item(4) & reader1.Item(5)
                        masiv(3) = reader1.Item(4)
                        masiv(4) = reader1.Item(6).ToString
                        Get_egn()
                        If vzemi_egn = "" Then
                            prehvyrlqne_ot_DGrid()
                        End If
                    End While
                    FlowLayoutPanel1.Visible = False
                    reader1.Close()

                End Using
            End Using
            '  Else : MsgBox("Файлът DataU не съществува в директорията " & DataDir1, MsgBoxStyle.Critical, "Не съществуваща БД")
        Else : MsgBox("Файлът Update не съществува", MsgBoxStyle.Critical, "Не съществуваща БД")
        End If
        'Else : MsgBox("Файлът Update не съществува", MsgBoxStyle.Critical, "Не съществуваща БД")
        'End If

    End Sub
  
    Private Sub prehvyrlqne_ot_DGrid()
        'If da Then
        Dim strCon As String
        Dim param1 As OleDbParameter
        Dim param2 As OleDbParameter
        Dim param3 As OleDbParameter
        Dim param4 As OleDbParameter
        Dim param5 As OleDbParameter
        strCon = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & strAcessFilePath1 & ";Jet OLEDB:Database Password=ipek0809;"
        Using theConnection As New OleDbConnection(strCon)
            ' OleDbConnection1 = New OleDbConnection(strCon)
            theConnection.Open()
            strQuery = "insert into uchenici (egn, stname, klas, klas_rim, adres) values(?,?,?,?,?)"
            ' Using cmd = New OleDbCommand("select", cn)

            Using OleDbCommand1 = New OleDbCommand(strQuery, theConnection)
                param1 = New OleDbParameter("@avtor", OleDbType.VarWChar, 100)
                param2 = New OleDbParameter("@egn", OleDbType.VarWChar, 100)
                param3 = New OleDbParameter("@egn1", OleDbType.VarWChar, 100)
                param4 = New OleDbParameter("@egn2", OleDbType.Integer)
                param5 = New OleDbParameter("@adres", OleDbType.VarWChar, 100)
                param1.Value = masiv(0)
                param2.Value = masiv(1)
                param3.Value = masiv(2)
                param4.Value = masiv(3)
                param5.Value = masiv(4).ToString
                OleDbCommand1.Parameters.Add(param1)
                OleDbCommand1.Parameters.Add(param2)
                OleDbCommand1.Parameters.Add(param3)
                OleDbCommand1.Parameters.Add(param4)
                OleDbCommand1.Parameters.Add(param5)
                OleDbCommand1.ExecuteNonQuery()
            End Using
        End Using
    End Sub

Public Sub Get_egn()
        Dim selectdata2 As String
        Dim param11 As OleDbParameter
        selectdata2 = "SELECT * FROM uchenici WHERE egn=?"
        Dim strConn As String
        strConn = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & strAcessFilePath1 & ";Jet OLEDB:Database Password=ipek0809;"
        OleDbConnection3 = New OleDbConnection(strConn)
        OleDbConnection3.Open()
        OleDbCommand3 = New OleDbCommand(selectdata2, OleDbConnection3)
        param11 = New OleDbParameter("@egn", OleDbType.VarWChar, 100)
        param11.Value = masiv(0)
        OleDbCommand3.Parameters.Add(param11)
        vzemi_egn = OleDbCommand3.ExecuteScalar
        OleDbCommand3.Dispose()
        OleDbConnection3.Close()
    End Sub

If CStr(cboCarrier.SelectedValue.ToString) = "99" Then
      tbCarrierDesc.Visible = True
         Else
      tbCarrierDesc.Visible = False
         End If
     End If

If Not cboCarrier.SelectedValue.ToString Is Nothing Then 'added this line
    If CStr(cboCarrier.SelectedValue.ToString) = "99" Then
        tbCarrierDesc.Visible = True
    Else
        tbCarrierDesc.Visible = False
    End If
End If