add click event to an imagebutton generated in listView

hi all, am quite new to asp.net am trying to implement an 'add to cart' button which is generated in a listView
on clicking the imagebutton am trying to add the the product id and quantity=1 to my sortedlist Session
i tried to use command argument but no success
am i doing it right ?

<asp:ListView  ID="listview1" GroupItemCount="3" runat="server">
        <LayoutTemplate>
            <div id="itemListView">
                <asp:PlaceHolder runat="server" ID="groupPlaceHolder" />
            </div>
        </LayoutTemplate>
        <GroupTemplate>
            <div style="clear: both;">
                <asp:PlaceHolder runat="server" ID="itemPlaceHolder" />
            </div>
        </GroupTemplate>
        <ItemTemplate>
            <div class="lvProduct">
                
               
                <div class="productDisplayImage">
                        <asp:Imagebutton  imageURl='<%# Eval("imageUrl") %>'
                       PostBackUrl= '<%#string.concat("~/productDetail.aspx?pid=",Eval("pid")) %>'
                       
                        width="175px" Height="160px" runat="server"/>
                        
                </div>
                
                <div class="productPriceDisplay">
                        Price: $<%# Eval("price")%> <asp:ImageButton imageUrl="~/assignment/images/addToCartButton.png" ImageAlign="top" 
 onCommand="addToCart" commandArgument= '<%#string.concat("Eval("pid")) %>'                        
                        Width="100px" height="25px" style="margin-left:10px;" runat="server"/>
                </div>
            </div>
        </ItemTemplate>
        <Itemseparatortemplate>
            <div class="itemSep">
            </div>
        </ItemSeparatorTemplate>
        <GroupSeparatorTemplate>
            <div class="groupSep">
            </div>
        </GroupSeparatorTemplate>
        <EmptyDataTemplate>
        </EmptyDataTemplate>
    </asp:ListView>

Protected Function addToCart(ByVal sender As Object, ByVal e As CommandEventArgs) As Integer



        Dim pid As String = e.CommandArgument.ToString


        If Not IsNothing(Session("cart")) Then
            Dim slCart As SortedList = CType(Session("cart"), SortedList)
            slCart.Add(pid, "1")
            Response.Redirect("~/testing.aspx")
        Else
            Dim slCart As New SortedList

            slCart.Add(pid, "1")
 Response.Redirect("~/testing.aspx")

        End If

        Return Nothing
    End Function

Tags: Visual Basic, ASP.NET