BasePage.cs

using System;
using System.Web.UI;

namespace WebApplication.template
{
    public class BasePage : Page
    {
        public BasePage()
        {
            HeaderControls = new ControlCollection(this);
            FooterControls = new ControlCollection(this);
        }

        protected ControlCollection FooterControls { get; set; }
        protected ControlCollection HeaderControls { get; set; }

        protected override void OnInit(EventArgs e)
        {
            base.OnInit(e);
            HeaderControls.Add(LoadControl("controls/header.ascx"));
            FooterControls.Add(LoadControl("controls/footer.ascx"));
        }

        protected override void Render(HtmlTextWriter writer)
        {
            RenderTemplate(HeaderControls, writer);
            base.Render(writer);
            RenderTemplate(FooterControls, writer);
        }

        private static void RenderTemplate(ControlCollection collection, HtmlTextWriter writer)
        {
            foreach (Control c in collection)
            {
                c.RenderControl(writer);
            }
        }
    }
}