Область видимости переменной - Visual Basic .NET

 Private Sub CmbSelector_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cmbSelector.SelectedIndexChanged
 
        Select Case cmbSelector.Text      
            Case "Количество поданных заявлений по отделениям"  ' Первый CASE
                Debug.Print(cmbSelector.Text)
                dtBegin = CStr(dtpBegin.Value) & " " & cmbHBegin.Text & ":" & cmbMBegin.Text  'Присвоение значения переменным
                dtEnd = CStr(dtpEnd.Value) & " " & cmbHEnd.Text & ":" & cmbMEnd.Text          'dtBegin и dtEnd
                Debug.Print(dtBegin)
                Debug.Print(dtEnd)
                'Dim strSql As String
                Dim DT As New Data.DataTable
                Dim DS As New DataSet
                Dim strSql As Odbc.OdbcCommand = New Odbc.OdbcCommand("select distinct" &
        " subdivisionname , count(subdivisionname)" &
        " from casehistories where createtime between '" & dtBegin & "' and  '" & dtEnd & "'" &
        " and operation  =0 and subdivisionname <> ''" &
        " group by subdivisionname order by count(subdivisionname)", cn) With {
                    .CommandType = CommandType.Text
        }

                ' MsgBox("connected!!!")
                Dim Sdap As Odbc.OdbcDataAdapter = New Odbc.OdbcDataAdapter With {
                    .SelectCommand = strSql
                                 }
 
                DS.Tables.Add(DT)
 
                Sdap.Fill(DT)
 
                DataGridView1.DataSource = (DT)
 
                cn.Close()
 
            Case "Общий отчет"      'Второй CASE
                Debug.Print(cmbSelector.Text)
                Dim DT As New Data.DataTable
                Dim DS As New DataSet
 
                Dim strSql As Odbc.OdbcCommand = New Odbc.OdbcCommand("SELECT DISTINCT" &
        " documentcases.registrationdate , documentcases.documentcaseno, customers_naturalcustomer.lastname, customers_naturalcustomer.firstname" &
        " From documentcases,customers_naturalcustomer" &
        " Where documentcases.registrationdate Between '" & dtBegin & "' and  '" & dtEnd & "'and customers_naturalcustomer.id = documentcases.customerid order by documentcases.registrationdate", cn)
 
               'Переменные dtBegin и dtEnd пустые!!!!!?
 
                DS.Tables.Add(DT)
 
                Call New Odbc.OdbcDataAdapter() With {
                .SelectCommand = strSql
                             }.Fill(DT)
 
                DataGridView1.DataSource = (DT)
 
                cn.Close()
 
        End Select
    End Sub