Making Personalization Properties Read-Only : Introduction « Profile « ASP.NET Tutorial

            <add name="StartDate" type="System.DateTime" readOnly="True" />           
    <authentication mode="Windows" />

15.5.1.Using Profiles
15.5.2.Get / set profile data defined in Web.config
15.5.3.Get / set user-defined object to profile
15.5.4.Inheriting a Profile from a Custom Class
15.5.5.Creating Complex Profile Properties
15.5.6.Making Personalization Properties Read-Only
15.5.7.Defining default values for personalization properties
15.5.8.Working with the automaticSaveEnabled attribute