Ho provato ora con questo codice:
codice:
public class MobileWebForm1 : System.Web.UI.MobileControls.MobilePage
	{
		protected System.Web.UI.MobileControls.Label Label1;
		protected System.Web.UI.MobileControls.Panel Panel1;
		protected System.Web.UI.MobileControls.SelectionList SelectionList1;
		protected System.Web.UI.MobileControls.Command Command1;
		protected System.Web.UI.MobileControls.Form Form1;

		private void Page_Load(object sender, System.EventArgs e)
		{
			if (!Page.IsPostBack)
			{
				SelectionList1.Items.Add("ciao");
				SelectionList1.Items.Add("ciao2");
				SelectionList1.Items.Add("ciao3");
			}
		}
		private void Command1_Click(object sender, System.EventArgs e)
		{
			Label1.Text=SelectionList1.Items[SelectionList1.SelectedIndex].Value;
		}
	}
Con questo codice html:
codice:
<body Xmlns:mobile="http://schemas.microsoft.com/Mobile/WebForm">
	<mobile:form id="Form1" runat="server" BackColor="White">
		<mobile:Panel id="Panel1" runat="server">
			<mobile:SelectionList id="SelectionList1" runat="server"></mobile:SelectionList>
			<mobile:Command id="Command1" runat="server">Command</mobile:Command>
				<mobile:Label id="Label1" runat="server" ForeColor="Red"></mobile:Label>
		</mobile:Panel>
	</mobile:form>
</body>
E funziona.

Ciao