I'm confused about how properties work within the designer.



If I have a form and I add a public property to the form, after I build the assembly, the property is there in the property window.



However, if I have a BO or a UserControl and I add a property, after I build the assembly, the property isn't in the property windows of the UserControl or BO itself. It will be in the property window of an instance I've dropped on a form or some other container, but not in the designer for the object itself. The property will also show up in the property window of any sub-classed objects.



So, what determines what ends up in that little property window?

A property defined on a control itself will never show up within a property designer.  The purpose of a control and a control property is for use on a parent container or form or object other than itself.  So these properties will only show up as an instance.  This actually makes a lot of sense as the logic behind these properties is going to happen within the instance. 

So like you mentioned, any defined properties on a control will not show up until created as an instance.  You can make properties show up on a control through a lot of work and editor logic....but I am not even going down this road on this thread as that is a HUGE conversation in and of itself.

OK, that makes some sense.



How does .NET determine this? Is it by inheritance? Things inheriting from component and control have this behavior?

Inheritance can play a factor.  For example if you add properties to a form then inherit that frorm, they will be visible wihtin the designer.  However, ifyou create a control and never inherit it, as soon as you drop it on a form those properties (as an instance) will be available within the designer.  Ultimately it comes down to when the object is created as an instance, even for design-time purposes.

Oh...I think the light bulb just went off!



So, when I look at a BO in design view, where I can get to the properties window, the BO I'm on isn't really being instantiated yet, thus properties of that BO aren't shown. The same for a control or component, because the control itself isn't instantiated by the designer of that control.



However, when plopped on a form or user control, the BO/control/component is instantiated by the designer and now the properties are available.



The reason that form/user control properties would show up in the designer is because the form/user control is actually instantiated by the designer, thus the properties are shown in that case.



I think that is what's going on in any case.

Yup...you got it