public partial class _Default : System.Web.UI.Page 
{
    protected void Page_PreInit(object sender, EventArgs e)
    {
        //this.DropDownList1.Items.Clear();
        Response.Write("Page_PreInit<br/>");

    }

    protected void Page_Init(object sender, EventArgs e)
    {
        //this.DropDownList1.Items.Clear();
        Response.Write("Page_Init<br/>");
    }

    protected void Page_Load(object sender, EventArgs e)
    {
        //this.DropDownList1.Items.Clear();
        Response.Write("Page_Load<br/>");
        Response.Write("IsPostback:" + IsPostBack.ToString()+"<br/>");
    }

    protected void Page_PreRender(object sender, EventArgs e)
    {
        //this.DropDownList1.Items.Clear();
        Response.Write("Page_PreRender<br/>");
    }

    protected void Page_Unload(object sender, EventArgs e)
    {
        this.DropDownList1.Items.Clear();
        //Response.Write("Page_Unload");
    }

}