Io sono curioso e certe volte testardo

Ho cambiato la mia paginetta di prova ed ho messo ESATTAMENTE il tuo codice. Ebbene, mi funziona :master:
Perciò la domanda, ma sei proprio sicuro che quei panel di quel nome esistano per davvero?
codice:
<%@ Page language="c#" %>
<%@ import namespace="Libreria" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" > 

<html>
  <head>
    <title>WebForm16</title>
    <meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">
    <meta name="CODE_LANGUAGE" Content="C#">
    <meta name=vs_defaultClientScript content="JavaScript">
    <meta name=vs_targetSchema content="http://schemas.microsoft.com/intellisense/ie5">
  </head>
  <body MS_POSITIONING="FlowLayout">
	
    <form id="Form1" method="post" runat="server">
			


				<asp:Button id="Button1" runat="server" Text="Button" OnClick="Button1_onclick"></asp:Button></P>
			

</P>
			<asp:Repeater id="Repeater1" runat="server" EnableViewState="False" OnItemCreated="Repeater1_ItemCreated">
				<ItemTemplate>
					<asp:Panel ID="alternatePriceContents" Runat="server">
						<%#((System.Data.Common.DbDataRecord)Container.DataItem)["NOME_REGIONE"]%>
						

					</asp:Panel>
					<asp:Panel ID="itemPriceContents" Runat="server">
						<%#((System.Data.Common.DbDataRecord)Container.DataItem)["CODICE_ISTAT_REGIONE"]%>
						

					</asp:Panel>
					
				</ItemTemplate>
				<AlternatingItemTemplate>
					<asp:Panel ID="alternatePriceContents" Runat="server" BackColor="yellow">
						<%#((System.Data.Common.DbDataRecord)Container.DataItem)["NOME_REGIONE"]%>
						

					</asp:Panel>
					<asp:Panel ID="itemPriceContents" Runat="server">
						<%#((System.Data.Common.DbDataRecord)Container.DataItem)["CODICE_ISTAT_REGIONE"]%>
						

					</asp:Panel>
					
				</AlternatingItemTemplate>
			</asp:Repeater>

     </form>
  </body>
</html>
<script runat="server">
private string StringaConnessione()
{
	return "Provider=Microsoft.Jet.OLEDB.4.0;Password='';User ID=Admin;Data Source=C:\\DATI\\test\\test.mdb;Mode=Share Deny None;Extended Properties='';Jet OLEDB:System database='';Jet OLEDB:Registry Path='';Jet OLEDB:Database Password='';Jet OLEDB:Engine Type=5;Jet OLEDB:Database Locking Mode=1;Jet OLEDB:Global Partial Bulk Ops=2;Jet OLEDB:Global Bulk Transactions=1;Jet OLEDB:New Database Password='';Jet OLEDB:Create System Database=False;Jet OLEDB:Encrypt Database=False;Jet OLEDB:Don't Copy Locale on Compact=False;Jet OLEDB:Compact Without Replica Repair=False;Jet OLEDB:SFP=False";
}

void Page_Load()
{
	if(!this.IsPostBack)
	{
		ModuloWeb.DataBind(this.Repeater1, StringaConnessione(), "select * from regioni");
	}
}


void Button1_onclick(object sender, System.EventArgs e)
{
	Session["user"] = "Pincus Pallinus";
	ModuloWeb.DataBind(this.Repeater1, StringaConnessione(), "select * from regioni");
}



void Repeater1_ItemCreated(object sender, RepeaterItemEventArgs e)
{
	/*
	switch(e.Item.ItemType)
	{
		case ListItemType.Item:
		case ListItemType.AlternatingItem:
		Panel Panel = (Panel) e.Item.FindControl("alternatePriceContents");
		if(!(Panel == null)) Panel.BackColor = System.Drawing.Color.Khaki;
		break;
	}
	*/

	if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem) 
	{ 
		if(Session["user"]==null) 
		{ 
			((Panel)e.Item.FindControl("alternatePriceContents")).Visible=false; 
			((Panel)e.Item.FindControl("itemPriceContents")).Visible=false; 
		} 
		else 
		{ 
			((Panel)e.Item.FindControl("alternatePriceContents")).Visible=true; 
			((Panel)e.Item.FindControl("itemPriceContents")).Visible=true; 
		} 
	} 	

}

</script>