Question

I have an abstract base class and two derived classes. The base class contains 6 properties which all can be maintained on a form.

The two derived classed both have 1 extra property. Those two properties can also be maintained on the same form.

In my form I have now code like this:

  btnSomething.visible = (myObject is DerivedA);
  pnlPanel.visible = !(myObject is DerivedA);

  if(myObject is DerivedA)
    myBindingSource.DataSource = myObject as DerivedA

  mySecondBindingSource = myObject;

I am not very happy with this approach, it smells. So my question is, what is a neat/good way to make this more OO? Because it is possibly that in the future DerivedC comes in…

I think this approach breaks the OCP principle (and probably other principles)

Answer 1

You can use polymorphism and inheritance here:

Define an interface

interface ICommonFeatures
{
    bool ContainsFoo {get;}
    //yak-yak
}

Then your derived classes implement it

class DerivedA: ICommonFeatures
{
    bool ContainsFoo {get {return true;}}
    //so-and-so
}
class DerivedB: ICommonFeatures
{
    bool ContainsFoo {get {return false;}}
    //this-and-that
}

And when you use it, you deal only with the interface

ICommonFeatures foo = new DerivedB();

btnSomething.visible = foo.ContainsFoo;
pnlPanel.visible = foo.Prop2;
myBindingSource.DataSource = foo.CurrentDataSource