trouble with sorting columns on gridview in ASP.NET 2.0

I am having trouble sorting columns on  a  gridview in ASP.NET 2.0.  
I finally got paging to work, but the sorting does not seem to do anything (not sure how I re-populate the datatable in the code behind).
The events are firing just fine, but I can't seem to make it work (because I am binding the GV with a button click instead of at design time):

                                            <asp:GridView ID="gvCommSummary" runat="server" EmptyDataText="No records found" AutoGenerateColumns="False" CellPadding="4"
                                                ForeColor="#333333" GridLines="None" HorizontalAlign="Left" PageSize="2" Width="600px" AllowPaging="True" AllowSorting="True" >
                                                <PagerSettings FirstPageText="&amp;lt;&amp;lt;First Page" LastPageText="Last Page&amp;gt;&amp;gt;" PageButtonCount="15" Position="TopAndBottom" Mode="NumericFirstLast" />
                                                <FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
                                                <RowStyle BackColor="#F7F6F3" ForeColor="#333333" />
                                                <Columns>
                                                    <asp:BoundField DataField="AffiliateID" HeaderText="Affiliate ID" ReadOnly="True" SortExpression="AffiliateID" >
                                                        <ItemStyle HorizontalAlign="Left" Width="100px" Wrap="False" />
                                                        <HeaderStyle Wrap="False" />
                                                    </asp:BoundField>
                                                    <asp:HyperLinkField DataNavigateUrlFields="AffiliateID" DataTextField="Name" HeaderText="Name"
                                                        Text="Name" DataNavigateUrlFormatString="editaffiliates.aspx?iden={0}" >
                                                        <ItemStyle HorizontalAlign="Left" Width="100px" Wrap="False" />
                                                        <HeaderStyle Wrap="False" />
                                                    </asp:HyperLinkField>
                                                    <asp:BoundField DataField="totalcommdue" DataFormatString="{0:c}" HeaderText="Comm Due" NullDisplayText="0" ReadOnly="True">
                                                        <ItemStyle HorizontalAlign="Right" Width="100px" Wrap="False" />
                                                        <HeaderStyle Wrap="False" />
                                                    </asp:BoundField>
                                                    <asp:BoundField DataField="totalcommbase" DataFormatString="{0:c}" HeaderText="Comm Basis" NullDisplayText="0" ReadOnly="True">
                                                        <ItemStyle HorizontalAlign="Right" Width="100px" Wrap="False" />
                                                        <HeaderStyle Wrap="False" />
                                                    </asp:BoundField>
                                                    <asp:BoundField DataField="totalcommpaid" DataFormatString="{0:c}" HeaderText="Comm Paid" NullDisplayText="0" ReadOnly="True">
                                                        <ItemStyle HorizontalAlign="Right" Width="100px" Wrap="False" />
                                                        <HeaderStyle Wrap="False" />
                                                    </asp:BoundField>
                                                    <asp:BoundField DataField="totalcommowed" DataFormatString="{0:c}" HeaderText="Comm Owed" ReadOnly="True">
                                                        <ItemStyle HorizontalAlign="Right" Width="100px" Wrap="False" />
                                                        <HeaderStyle Wrap="False" />
                                                    </asp:BoundField>
                                                </Columns>
                                                <PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" />
                                                <SelectedRowStyle BackColor="#E2DED6" Font-Bold="True" ForeColor="#333333" Wrap="False" />
                                                <HeaderStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
                                                <EditRowStyle BackColor="#999999" />
                                                <AlternatingRowStyle BackColor="White" ForeColor="#284775" />
                                            </asp:GridView>Start Free Trial

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Partial Class affiliatecomm
        Inherits System.Web.UI.Page
 
        Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
            'Response.CacheControl = "private"
            'Response.Expires = 0
            'Response.AddHeader("pragma", "no-cache")   
 
        End Sub
 
        Protected Sub btnGetAffCommData_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnGetAffCommData.Click
            Me.PopulateAffSummData()
        End Sub
 
        Protected Sub PopulateAffSummData()
            Dim ds As DataSet = DB.GetDS("dbo.AffCommDueSummary", False)
 
            If ds.Tables(0).Rows.Count > 0 Then
                Me.gvCommSummary.DataSource = ds.Tables(0)
                Me.gvCommSummary.DataBind()
            End If
 
        End Sub
 
        Private Function ConvertSortDirectionToSql(ByVal sortDirection As SortDirection) As String
            Dim NewSortDirection As String = String.Empty
            Select Case sortDirection
                Case sortDirection.Ascending
                    NewSortDirection = "ASC"
                Case sortDirection.Descending
                    NewSortDirection = "DESC"
                Case Else
                    NewSortDirection = ""
            End Select
            Return NewSortDirection
        End Function
 
        Protected Sub gvCommSummary_PageIndexChanging(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewPageEventArgs) Handles gvCommSummary.PageIndexChanging
            Me.PopulateAffSummData()
 
            gvCommSummary.PageIndex = e.NewPageIndex
            gvCommSummary.DataBind()
        End Sub
 
        Protected Sub gvCommSummary_Sorting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewSortEventArgs) Handles gvCommSummary.Sorting
            Me.PopulateAffSummData()
 
            Dim dt As DataTable = gvCommSummary.DataSource
 
            If Not dt Is Nothing Then
                Dim dataView As DataView = New DataView(dt)
                dataView.Sort = e.SortExpression + " " + ConvertSortDirectionToSql(e.SortDirection)
 
                gvCommSummary.DataSource = dataView
                gvCommSummary.DataBind()
            End If
        End Sub
    End Class