Btn.PostBackUrl / Nested with DropDownList INSIDE a Datalist

Question

in VB.net I have a DATALIST in which, among others I have a DropDL CTRL which is Bound with LINQ something like this:

Public Sub DLCategorias_ItemDataBound(sender As Object, e As System.Web.UI.WebControls.DataListItemEventArgs) Handles DLCategorias.ItemDataBound

If e.Item.ItemType = ListItemType.AlternatingItem Or e.Item.ItemType = ListItemType.Item Then

Dim DC As New MyDataContext
Dim cat = (From c In FF.ProductosCategorias Select c Where c.idCategoria = (CTypeDLCategorias.DataKeys(e.Item.ItemIndex), Integer))).Single
        
Dim thisId As Integer = cat.idCategoria
Dim subcat = From d In dc.ProductosSubCategorias Where d.idCategoria = thisId Select d.idSubCategoria, d.NombreSubCategoria

Dim ddlSubCat As DropDownList = CType(e.Item.FindControl("ddlSubCat"), DropDownList)
Dim BTNVER As Button = CType(e.Item.FindControl("BtnVerSubCat"), Button)

ddlSubCat.DataTextField = "NombreSubCategoria"
ddlSubCat.DataValueField = "idSubCategoria"
ddlSubCat.DataSource = subcat
ddlSubCat.DataBind()
ddlSubCat.AutoPostBack = True  
        
BTNVER.PostBackUrl = "SubCat.aspx?idSubCategoria=" & ddlSubCat.SelectedValue.ToString

What I am trying to achieve is that IF ddlSubCat has its value changed (cause some user selected another SubCat to see) the POSTBACK get working fine.

What it does (up to here) is getting the FIRST value of DDLSubCat (first index of DDL) I need to SOMEHOW "refresh" (but can't) de DATABOUND or whatever for the Button Works fine.

Tried everything, did ONCLICK (but the ddlSubCat does not appear in codebehing since its in DL) Tried to EVAL in Design view... BUT CAN'T!

Answer 1

SOLVED ! Thanks to som other answer from Tim Schmelter, I realice that I could be handled by Codebehind in the BTN click event like this:

Protected Sub BtnVerSubCat_Click(sender As Object, e As EventArgs)

    Dim container = DirectCast(DirectCast(sender, Control).NamingContainer, DataListItem)
    Dim idSubCat = DirectCast(container.FindControl("ddlSubCat"), DropDownList)
    Dim Xid As String = idSubCat.SelectedValue
    Response.Redirect("SubCat.aspx?idSubCatgoria=" & Xid)

End Sub

Thanks anyway