C# - Creating A Custom Datatype In Umbraco?

I am trying to create a custom datatype. The intention being a dropdown list. As of right now, I can access the control I created but no properties or values are showing up within it. Just the blank drop down.

public partial class usercontrols_admin_customDataType_CountryDropDown :
System.Web.UI.UserControl,
umbraco.editorControls.userControlGrapper.IUsercontrolDataEditor
{
public string umbracoValue;
protected void Page_Load(object sender, EventArgs e)
{
if (Page.IsPostBack)
{
DataSet ds = new DataSet();
FormFieldBuilder countries = new FormFieldBuilder();
ds = countries.GetAllCountries();
ddCountries.DataSource = ds;
ddCountries.DataTextField = ds.Tables[0].Columns["DisplayName"].ToString();
ddCountries.DataValueField = ds.Tables[0].Columns["guiCountryID"].ToString();
ddCountries.DataBind();
}
}
#region IUsercontrolDataEditor Members
public object value
{
get
{
return ddCountries.SelectedValue;
}
set
{
if (value != null)
{
ddCountries.SelectedValue = value.ToString();
}
}
}
#endregion
}