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.NET Forum / Windows Forms / WinForm General / January 2008Can control properties on base Form be changed on derived Form?
Hi, When I have a base Form that I add controls to, then inherit that Form, when the derived class is viewed in the designer, the controls that were placed on the base are visible, but all the properties are locked. What I would like to do is to use controls in the base that act like a template where the base has certain (default) controls defined, but then the subforms to override some or all of those properties. For instance, suppose a Label was placed on the base Form at some default location, I would still like the derived class to be able to move. Another example is if I have a ListView that has some default columns defined. I would like the derived class to be able to add more columns if necessary. Is this possible within the constraints of VS's designer support? Have you tried changing the Modifiers property of each control in the designer property grid? By default, all controls are private, which means the derived class won't be able to access them. If you change it to an appropriate non-private value, the derived class should be able to modify the properties of the controls. > Hi, > [quoted text clipped - 11 lines] > > Is this possible within the constraints of VS's designer support? Great, this works. A related questions. In the scenario I laid out, is it possible to have the derived form told to "delete" the control eventhough the base is still defining it. I have seen that I can change the properties of controls defined in the base Form, but when I select one of those and try to remove it from the designer, no good. > Have you tried changing the Modifiers property of each control in the > designer property grid? By default, all controls are private, which means [quoted text clipped - 24 lines] >> >> Is this possible within the constraints of VS's designer support? You cannot remove members of a base class as far as I know. Once a member is inherited it will always be present. In a way, it's as if a derived class is an instance of two classes: one of the base class and one of itself. Still, you could set the Visible property of the controls you do not want to display to false. This would keep them from being displayed on the derived form. It *might* be a memory-saver to dispose of them as well in your derived constructor or Load event, but that could be a mistake if there's anything in the base class that accesses the control. I'd test disposing the control heavily before releasing something like that. > Great, this works. > [quoted text clipped - 3 lines] > defined in the base Form, but when I select one of those and try to remove > it from the designer, no good. > A related questions. In the scenario I laid out, is it possible to have > the derived form told to "delete" the control eventhough the base is still > defining it. I have seen that I can change the properties of controls > defined in the base Form, but when I select one of those and try to remove > it from the designer, no good. You cannot delete controls (or any other properties, methods, fields) from an inherited form (class). You could set the control's visible property to false making it appear to be gone as opellegr replied. However another option in this case is to use Item/Project Templates as opposed to Class Inheritance. The templates can be used to create a new form with a base set of controls you commonly use but also allow you to delete controls, properities, methods and fields that you don't need for the created instance. I actually prefer templates over inheritance in most cases for common forms and project types. hth -- Gregg Walker
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