I am creating custom data type in umbraco (based on this article) and am using DataEditorSetting attribute for a property.

The problem is I'm getting DataEditorSetting could not be found... and I don't know what assembly I should reference to have it included in my project.

The code goes like this:

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;

using umbraco.cms.businesslogic.datatype;


namespace UmbracoCreateCustomDatatypeWithWrapper
{
    public partial class Demo : System.Web.UI.UserControl, umbraco.editorControls.userControlGrapper.IUsercontrolDataEditor  
{
    public string umbracoValue;
    public object value
    {
        get
        {
            return umbracoValue;
        }
        set
        {
            umbracoValue = value.ToString();
        }
    }

            [DataEditorSetting("Text column")]
            public string TextColumn { get; set; }
    }
}

I have referenced umbraco, umbraco.editorControls & cms. What am I missing?