I need to insert a ISettingControl (dropdownlist or ListBox) whose elements are loaded from a database.

The loading is successful, but when retrieving the selected value that is null.
Below is the code implemented.

<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="ListPagesSetting.ascx.cs" Inherits="srdE20.Web.UI.ListPagesSetting" %>

<asp:ListBox ID="ddPages" runat="server" SelectionMode="Single" >

</asp:ListBox>

         private void PopulateControls()
        {
            DataTable dt = srdE20_CalendarEvent.GetPages();
            this.ddPages.DataSource = dt;
            ddPages.DataTextField = "PageName";
            ddPages.DataValueField = "PageId";
            ddPages.DataBind();
        }

      #region ISettingControl

            
            public string GetValue()
            {
                return ddPages.SelectedValue;
            }

            public void SetValue(string val)
            {
                if (ddPages.Items.Count == 0)
                {
                    PopulateControls();
                }
                
                ListItem item = ddPages.Items.FindByValue(val);
                if (item != null)
                {
                    ddPages.ClearSelection();
                    item.Selected = true;
                    //txtValue.Text = val;
                }
            }

        #endregion

when I access the settings page, the control is properly populated. But when I saving the data no value is selected, indeed it would seem that the control is no longer populated

Can anyone suggest me where am I wrong

I apologize for my bad english :)