The type or namespace name 'UITypeEditor' could not be found (are you missing a using directive or an assembly reference?)

I placed this in my BO Base, along with other code that seems to be working but when it comes to this line I get this error above.

Here are my USING statements in the BaseBO:

using

MicroFour.StrataFrame.Business;

using

System;

using

System.Collections;

using

System.Collections.Generic;

using

System.ComponentModel;

using

System.Data;

using

System.Data.SqlClient;

using

System.Runtime.Serialization;

using

System.Text;

using

MicroFour.StrataFrame.Security;

using

System.Diagnostics;

using

Microsoft.VisualBasic;

using

System.ComponentModel.Design;

using

System.Collections.Specialized;

using

System.Reflection;

using

System.Runtime.InteropServices.ComTypes;

using

MicroFour.StrataFrame.UI.Windows.Forms;

using

MicroFour.StrataFrame.Extensibility;

using

System.Drawing.Design;

[Category(BUSINESSRULES_CATEGORY_NAME), Description("The AuditFieldsCollection that defines the fields within the business object that are required. If a required field is not populated, then a broken rule will be automatically added to the business object."), DesignerSerializationVisibility(DesignerSerializationVisibility.Content), Editor(Constants.TE_RequiredFieldsEditor, typeof(UITypeEditor)]

public virtual RequiredFieldsCollection AuditFields

{

Get



{

return _AuditFields;



}



set { _AuditFields = value; }



}