I've created an umbrac usercontrol wrapper Data Type which wraps a DropDownList populated with data from a database.  I have the Database datatype for the Umbraco Data Type set to "Integer", which is correct to the Value property on the item in the DropDownList (an int primary key).

I can select the value from the data type within the document and save correctly.  This is verified by rending the value of the control on the page.

<umbraco:Item field="circuitId" runat="server"></umbraco:Item>

However, when I move to a different document and come back to the original, the value displayed in the drop down list list is the first item in the list.

My Usercontrol codebehind is this:

    public partial class CircuitsDataType : System.Web.UI.UserControl, umbraco.editorControls.userControlGrapper.IUsercontrolDataEditor
    {
        private ICircuitRepository _circuitRepository;

        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack) {

                var circuits = _circuitRepository.GetAll();

                CircuitList.DataSource = circuits;
                CircuitList.DataValueField = "Id";
                CircuitList.DataTextField = "Name";
                CircuitList.DataBind();

            }
        }

        protected override void OnInit(EventArgs e)
        {
            base.OnInit(e);

            _circuitRepository = new CircuitRepository();
        }

        public object value
        {
            get { return CircuitList.SelectedValue; }
            set
            {                
                CircuitList.SelectedIndex = -1;
                var item = CircuitList.Items.FindByValue(value.ToString());
                if (item != null) item.Selected = true;

            }
        }        
    }

It appears as if the underlying circuitId on the Document is not getting passed into the value property from IUsercontrolDataEditor.

Also, for extra points ( :p ) can someone remind me the correct way to do this:

<umbraco:Macro CircuitId='<umbraco:Item field="circuitId" runat="server"></umbraco:Item>' Alias="F1CircuitDetail" runat="server"></umbraco:Macro>