Custom Control resets on postback

Here is the page code:
<%@ Register Namespace="Company.Web.UI.WebControls" Assembly="Company.Web.UI.WebControls" tagprefix="Company" %>
 
<Company:DropDownListState ShowInstructionalOption="true" ShowFullList="true" ID="ddlState" runat="server" />
 
 
the control code:
	[ToolboxData("<{0}:DropDownListState runat=server></{0}:DropDownListState>")]
	public class DropDownListState : DropDownList
	{
		#region ================================= Public Properties =================================
 
		private int organizationId;
		public int OrganizationId
		{
			get
			{
				return organizationId;
			}
			set
			{
				organizationId = value;
			}
		}
 
		private int carrierId;
		public int CarrierId
		{
			get
			{
				return carrierId;
			}
			set
			{
				carrierId = value;
			}
		}
 
		private bool showFullList;
		public bool ShowFullList
		{
			get
			{
				return showFullList;
			}
			set
			{
				showFullList = value;
			}
		}
 
		private bool showInstructionalOption;
		public bool ShowInstructionalOption
		{
			get
			{
				return showInstructionalOption;
			}
			set
			{
				showInstructionalOption = value;
			}
		}
 
		#endregion
 
		#region ================================= Protected Events =================================
 
		protected override void OnLoad(EventArgs e)
		{
			base.OnLoad(e);
 
			bool hasResults;
 
 
			if (ShowFullList)
				this.DataSource = State.GetStateList(out hasResults);
			else
				this.DataSource = State.GetStateList(OrganizationId, CarrierId, out hasResults);
 
			if (hasResults)
			{
				this.DataTextField = "Value";
				this.DataValueField = "Key";
				this.DataBind();
 
				if (ShowInstructionalOption)
					this.Items.Insert(0, new ListItem("Select a State", "-1"));
			}
			else
			{
				this.Items.Clear();
				this.Items.Add(new ListItem("No States Available", "-1"));
			}
 
			ViewState.Add("SelectedIndex", base.SelectedIndex);
		}
		#endregion
	}

                                              

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