ASP.NET - Keep DropDownList selection on repeater DataBound - asp.net

Question

I have two DropDownLists per item on a Repeater.
I am binding both lists to two different lists on the repeater DataBound.
Both lists have an OnSelectedIndexChanged event handler which does some calculations based on the selections in both DropDownLists. Both lists also have AutoPostBack="True".
I need the calculation to be updated immediately. So I added another data binding for the repeater - on the lists' event handler.
This is the problem however - the repeater "resets" the selections to -1 and eventually the first items in both DropDownLists are displayed.
How can I make sure the selections remain after the data binding?
Here is the repeater structure:
<asp:Repeater runat="server" ID="rptCart">
<ItemTemplate>
<tr>
<td class="size"><div><asp:DropDownList runat="server" ID="_selectSize" AutoPostBack="true" OnSelectedIndexChanged="selectChange" EnableViewState="true" TabIndex="<%#Container.ItemIndex%>"></asp:DropDownList></div></td>
<td class="material"><div><asp:DropDownList runat="server" ID="_selectMaterial" AutoPostBack="true" OnSelectedIndexChanged="selectChange" EnableViewState="true" TabIndex="<%#Container.ItemIndex%>"></asp:DropDownList></div></td>
</tr>
</ItemTemplate>
</asp:Repeater>
And the repeater DataBound:
Protected Sub rptCart_ItemDataBound(sender As Object, e As System.Web.UI.WebControls.RepeaterItemEventArgs) Handles rptCart.ItemDataBound
If e.Item.ItemType = ListItemType.AlternatingItem OrElse e.Item.ItemType = ListItemType.Item Then
Dim sizeSelect As DropDownList = CType(e.Item.FindControl("_selectSize"), DropDownList)
Dim materialSelect As DropDownList = CType(e.Item.FindControl("_selectMaterial"), DropDownList)
sizeSelect.DataSource = sizeList
sizeSelect.DataBind()
materialSelect.DataSource = materialList
materialSelect.DataBind()
End If
End Sub
And finally the DropDownLists event handler:
Protected Sub selectChange(ByVal sender As DropDownList, ByVal e As System.EventArgs)
Dim listing As New PriceListing
Dim ddl As DropDownList
Dim selectedIndex As Integer
If sender.ID = "_selectSize" Then
For Each rptrItem As RepeaterItem In rptCart.Items
ddl = CType(rptrItem.FindControl("_selectMaterial"), DropDownList)
If ddl.TabIndex = sender.TabIndex Then Exit For
Next
For Each listing In artDecoPricing
If listing.Size = sender.SelectedValue Then Exit For
Next
selectedIndex = ddl.SelectedIndex
ElseIf sender.ID = "_selectMaterial" Then
For Each rptrItem As RepeaterItem In rptCart.Items
ddl = CType(rptrItem.FindControl("_selectSize"), DropDownList)
If ddl.TabIndex = sender.TabIndex Then Exit For
Next
For Each listing In artDecoPricing
If listing.Size = ddl.SelectedValue Then Exit For
Next
selectedIndex = sender.SelectedIndex
End If
Select Case selectedIndex
Case 0
Cart.Order.Items(sender.TabIndex).PriceUnit = listing.Canvas
Case 1
Cart.Order.Items(sender.TabIndex).PriceUnit = listing.Acrylic
Case 2
Cart.Order.Items(sender.TabIndex).PriceUnit = listing.Framed
Case 3
Cart.Order.Items(sender.TabIndex).PriceUnit = listing.Framed
End Select
Cart.SaveOrder()
rptCart.DataSource = Cart.Order.Items
rptCart.DataBind()
End Sub
Thank you very much in advance!

Answer 1

You could store the old selection:
Dim sizeSelect As DropDownList = CType(e.Item.FindControl("_selectSize"), DropDownList)
Dim materialSelect As DropDownList = CType(e.Item.FindControl("_selectMaterial"), DropDownList)
Dim sizeSelectedIndex = sizeSelect.SelectedIndex
Dim materialSelectedIndex = materialSelect.SelectedIndex
' do the databinding ... '
sizeSelect.SelectedIndex = If(sizeSelectedIndex < sizeSelect.Items.Count -1, sizeSelectedIndex, -1)
materialSelect.SelectedIndex = If(materialSelectedIndex < materialSelect.Items.Count -1, materialSelectedIndex, -1)