<asp:GridView ID="GridView1" runat="server" DataSourceID="SqlDS_tabella" EnableSortingAndPagingCallbacks="true" EnableViewState="true" ShowFooter="true"  AutoGenerateColumns="true" AllowSorting="True" />

      
 Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        
        If Me.IsPostBack() Then
            Try
                Dim sSQL As String
                sSQL = ViewState("MySQL")
                SqlDS_tabella.SelectCommand = sSQL
            Catch ex As Exception
                ClientScript.RegisterStartupScript(Me.[GetType](), "myalert", "alert('" & ex.Message & "');", True)
            End Try

        End If
End Sub

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
 Try

        
        Dim Where As String = String.Empty
        Dim sSQL As String = String.Empty

       
        Select Case op_anno.SelectedValue.ToString
             Where = " WHERE anno " & op_anno.SelectedValue.ToString & " " & ddlanno1.SelectedValue.ToString & " AND " & " " & ddlanno2.SelectedValue.ToString
        End Select

       
        'stringa select e group by per View
        Dim SelectGroupby As String = String.Empty
        SelectGroupby = Replace(campi.SelectedValueList.ToString, "'", "")

        'se non ci sono campi nella select e group by esco !
        If String.IsNullOrEmpty(SelectGroupby) Then
            Dim myInfo As String = "nessun campo da visualizzare selezionato!"
            ClientScript.RegisterStartupScript(Me.[GetType](), "myalert", "alert('" & myInfo & "');", True)
            Exit Sub
        End If

        sSQL = " SELECT " & SelectGroupby & ", SUM(importo) as ordinato... " & _
                       " FROM (SELECT anno, ..., ...," & _
                       " ..." & _
                       " FROM tab_ordinato " & Where & ") Tab " & _
                       " GROUP BY " & SelectGroupby

        ' Response.Write(sSQL.ToString)

        ' per aggiungere campi inserire AUTOGENERATECOLUMNS="FALSE"
        ' For Each li As ListItem In campi.Items
        ' If li.Selected = True Then
        ' GridView1.Columns.Add(New BoundField() With {.DataField = li.ToString, .HeaderText = li.ToString})
        ' End If
        ' Next
       

       
        SqlDS_tabella.SelectCommand = sSQL
        ViewState("MySQL") = sSQL
       

        Catch ex As Exception
            lbl_err_sql.Text = ex.Message
        End Try

    End Sub