How can I edit the properties of a button in a form, where the button is on a custom user control?

Question

I have a custom user control, onto which I place a button control. I set the access modifier of the button to Public. When I drop the user control onto a form, I see the button, but am not able to select it or edit its properties in the form designer.

Ultimately, I want to create a far more complex custom wizard control, with a content panel, "Back" and "Next" buttons, etc. I have successfully created a content panel to which controls can be dropped into at design time on the main form.

However, I am bulked at not being able to edit nested controls on the user control itself.

When inheriting from a user control, or inheriting from a form, one can typically edit properties of controls whose access modifier is set to "Protected".

What do I need to do to be able to access controls of the custom user control from the designer of the form?

Answer 1

I think you need go to the user control designer view to modify the properties of the button (instead of the form where the user control is placed), since it is nested in the user control.

Answer 2

You can make basic changes to a child control of a user control on a form to the limited extent that you can expose the properties of interest via the parent user control designer and support the property changes at design time. You can make much more complex design time behaviors by writing your own custom designers but that is a potentially difficult to very difficult undertaking.

There is a good reason why it does not work the way you probably think it could and should and if you think about it carefully enough for a while, you will understand why. When you inherit from an object, yes you can change properties etc, but in this case you are creating a new type, so you can modify, add, redefine properties.

But when you drop a user control on a form, you are not creating a new type. You are creating an instance of a type, the user control, that is already defined. To the extent you can modify properties, you are modifying state that must be preserved for that instance. State must not only be persisted, but user controls also often involve painting etc so state changes can also have complex behavioral effects and this is a potentially complicated requirement that cannot be completely generalized.

So there are some modifications that are not possible at all, because they imply modifying the type, and you already have a type, you are only creating an instance. For the rest of the possible range of modifications that are ultimately state based, the platform only supports so much of the total possible state management.