Help with ASP.NET Server Custom Control

Hi guys, I am having problem collecting data from the viewstate I thought I was doing the correct coding to capture the value selected from a custom dropdownlist control but apparently I am not here it goes my custom control code

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace myFirstListingControl
{  
    [DefaultProperty("Text")]
    [ToolboxData("<{0}:YearListing runat=server>")]
    public class YearListing : WebControl
    {
       
        [Bindable(true)]
        [Category("Appearance")]
        [DefaultValue("")]
        [Localizable(true)]
        public string Text
        {
            get
            {                   
                String s = (String)ViewState["Text"];               
                //return ((s == null) ? "[" + this.ID + "]" : s);               
                return (s == null) ? String.Empty : s;               
            }
            set
            {
                ViewState["Text"] = value;
            }
        }       
        DropDownList _ddlPeriodYear = new DropDownList();
        protected override void RenderContents(HtmlTextWriter output)
        {           
            BuildDropDownYearListingControl(0);           
            _ddlPeriodYear.RenderControl(output);
            LoadDataFromViewState();    
        }
        //---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
        //- Return a drop-downlist control with 3 years worth of databound. (Inside the toolbar)
        //---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
        protected void BuildDropDownYearListingControl(int pNumberOfYear)
        {
            _ddlPeriodYear.EnableViewState = true;
            _ddlPeriodYear.ID = this.ID;
   _ddlPeriodYear.Text = this.Text;
            _ddlPeriodYear.AutoPostBack = true;
            //--_ddlPeriodYear.Style["width"] = "250px";
            _ddlPeriodYear.Items.Clear();
            //- 3 Years worth of year data.
            if (pNumberOfYear == 0)
            {
                _ddlPeriodYear.Items.Add(DateTime.Now.AddYears(-2).Year.ToString());
                _ddlPeriodYear.Items.Add(DateTime.Now.AddYears(-1).Year.ToString());               
            }
            else
            {
                for (int iYears = 1; iYears <= pNumberOfYear; iYears++)
                {
                    _ddlPeriodYear.Items.Add(DateTime.Now.AddYears(-(pNumberOfYear-iYears)).Year.ToString());
                }               
            }
            _ddlPeriodYear.Items.Add(DateTime.Now.Year.ToString());
            _ddlPeriodYear.SelectedValue = DateTime.Now.Year.ToString();           
            this.Controls.Add(_ddlPeriodYear);           
        }
  private void LoadDataFromViewState()
        {
            if (this.Context != null)
            {
                foreach (string key in this.Page.Request.Form.AllKeys)
                {
                    if (key.ToLower().Contains(this._ddlPeriodYear.UniqueID.ToLower()))
                    {
                        this.Text = this.Page.Request.Form[key];                       
                    }
                }
            }
        }
    }
}