Extracting from a list.

nlowdon

Good afternoon all, I'm learning to work with 'Lists' I've set up a list of 'zooAnimals' and in the list i've added objects as they have been created.

        zooAnimals = new List<Animal>();

        
        newcat1 = new Cat(cat1, catPen, fircat);
        newcat2 = new Cat(cat2, catPen, seccat);

        newtig1 = new Tiger(tiger1, tigerPen, firtig);
        newtig2 = new Tiger(tiger2, tigerPen, sectig);

        zooAnimals.Add(newcat1);
        zooAnimals.Add(newcat2);

        zooAnimals.Add(newtig1);
        zooAnimals.Add(newtig2);

I would like to now step through the list to perform certain actions when a button is pressed. For example - the form has a number of buttons on it - 1 being for individual groups of animals to eat(). I tried with

        foreach (Cat thisCat in zooAnimals)
        {
            if (thisCat.hunger == 7)
            {
                thisCat.hunger = thisCat.hunger - 5;
            }
        }

but this code throws an InvalidCast Exception...... Unable to cast object of type 'Zoo_Animals.Tiger' to type 'Zoo_Animals.Cat'. Is there a way of stepping through the list to do this ? Thanks in advance ! Neil

J4amieC

If you're using .NET 3.5 you can use

foreach(Cat thisCat in zooAnimals.OfType<Cat>())
{
...
}

otherwise you'll have to check each item

foreach(Animal animal in zooAnimals)
{
if(animal is Cat)
{
...
}
}

nlowdon

Thank you very much indeed - worked a treat !

Malcolm Smart

J4amieC wrote:

foreach(Cat thisCat in zooAnimals.OfType())

That's neat - and my trigger to start looking at 3.5 finally...

Knowledge is hereditary, it will find its way up or down. Luc Pattyn
and since what every time when i want to add button to this control one add two times posted in C# forum

Lost User

Yeah, didn't know about the OfType extension too, looks really useful in this situation.