Question

I have a few Abstract classes that have the core functionality of some UserControls in my project. I also have two separate implementations both deriving from the Abstract classes; lets call them AbstractImpl1 and AbstractImpl2. In addition, I have Collections of the Abstract UserControls that I iterate through in several places.

The issue I’m having is InvalidCastExceptions – I need to iterate through the implementations rather than the abstact UserControls to get to certain properties (visual). Is there a clean way of dealing with this other than doing a try/catch?

Example:

In my project I have Abstract classes: AbsUserControl
Then I have two separate implementations of them: AbstractImpl1 and AbstractImpl2

In my main form I have ObservableCollection<AbsUserControl> absControlCollection and then iterating through items I do foreach(AbstractImpl1 userControl in absControlCollection) to be able to access the visual aspects. The issue is that ObservableCollection<AbsUserControl> absControlCollection could either be comprised of AbstractImpl1 or AbstractImpl2 objects.

Is there a clean way of dealing with this? Right now, every place I iterate through the objects in absControlCollection I surround it with a try/catch block, trying to iterate through AbstractImpl1 objects then catching an InvalidCastException and proceeding with iterating through AbstractImpl2 objects.

Let me know if any more information is needed. Thanks!

Answer 1

An alternative to OfType; casting without exceptions:

foreach(AbsUserControl control in absControlCollection)
{
    if(control is AbstractImpl1)
    {
        AbstractImpl1 i1 = (AbstractImpl1)control;
        DoStuff(i1);
    }
    if(control is AbstractImpl2)
    {
        AbstractImpl2 i2 = (AbstractImpl2)control;
        DoOtherStuff(i2);
    }
}