I engaged a problem with inherited Controls in Windows Forms and need some advice on it.
I do use a base class for items in a List (selfmade GUI list made of a panel) and some inherited controls that are for each type of data that could be added to the list.
There was no problem with it, but I now found out, that it would be right, to make the base-control an abstract class, since it has methods, that need to be implemented in all inherited controls, called from the code inside the base-control, but must not and can not be implemented in the base class.
When I mark the base-control as abstract, the Visual Studio 2008 Designer refuses to load the window.
Is there a way to get the Designer work with the base-control made abstract?
I KNEW there had to be a way to do this (and I found a way to do this cleanly). Sheng's solution is exactly what I came up with as a temporary workaround but after a friend pointed out that the
Form class eventually inherited from an
abstract class, we SHOULD be able to get this done. If they can do it, we can do it.
We went from this code to the problem
Form1 : Form
public class Form1 : BaseForm ... public abstract class BaseForm : Form
This is where the initial question came into play. As said before, a friend pointed out that
System.Windows.Forms.Form implements a base class that is abstract. We were able to find...
public class Form1 : MiddleClass ... public class MiddleClass : BaseForm ... public abstract class BaseForm : Form ...
This actually works and the designer renders it fine, problem solved.... except you have an extra level of inheritance in your production application that was only necessary because of an inadequacy in the winforms designer!
This isn't a 100% surefire solution but its pretty good. Basically you use
#if DEBUG to come up with the refined solution.
#if DEBUG public class Form1 : MiddleClass #else public class Form1 : BaseForm #endif ...
public class MiddleClass : BaseForm ...
public abstract class BaseForm : Form ...
What this does is only use the solution outlined in "initial solution", if it is in debug mode. The idea is that you will never release production mode via a debug build and that you will always design in debug mode.
The designer will always run against the code built in the current mode, so you cannot use the designer in release mode. However, as long as you design in debug mode and release the code built in release mode, you are good to go.
The only surefire solution would be if you can test for design mode via a preprocessor directive.