The Load method is static, and cannot be overridden. None of the constructors will actually load the user data for you, so you'll never get an initialized object if you inherit from it. You need to wrap the UserSid object inside your own object, and expose the same properties, passing those to the inner object. Persisting through PersonalizedData is a good idea. In order to extend the information page in Admin mode you need to create a SidSettings plug-in, available from 4.50. See the SDK for more information (there are also some posts here about this topic.) /Steve

I've tried using your suggestions, but I don't understand the part concerning UserSid. I've been able to create a SidPlugin that displays a new tab when creating/editing users. But I've not been able to add custom fields to the existing Information page. Isn't this possible?

No, adding custom fields to the existing information page is not possible. That is partly why the SidPlugin feature was introduced. My post was about inheriting from UserSid, which will not give the effect the original poster was looking for. You should put your custom fields in your plug-in instead. /Steve

Thank you. Our plugin uses required field validators. If the user only fills out fields on the Information page and then saves, nothing happens (because of the validator). This is however not visible untill the user access the plugin page. Do you have any suggestions on how to display messages to the user regardless of which sub page he or she is on? Perhaps by using the message area at the top of the edit page?

What happens if you use the validation summary that already exists there (id = Summary)? See /edit/usersettings.ascx. It is the same user control that is used in /admin too. /Steve

Not sure if that is a good solution. First: The user controls employ the INamingContainer interface, so the summary's correct ID is "_Innercontrol_Summary". Guess we can't make the assumption that it will stay this way forever. Second: There is no info on how this summary works. It belongs to the SystemControls namespace, which is not documentet in the SDK.

Question: If the control with ID = Summary is a validation summary; how can I make my validators use it? I've tried using the validators within the SystemControls namespace, but no message is displayed in the summary. I guess the plug in control runs within the UserSettings.asmx control hierarchy, so that the summary is accessible (since the buttons from the information page is displayed correctly).

I found the error. Using Reflector I discovered that the ValidationSummary found in SystemControls needs a postback (it checks the Page.IsValid for validation errors). So when setting the EnableClientScript on the validator to false, everything worked okey.