Question

I have two lists. The types of both lists inherit from the same base type. I want to iterate through them and do operations which only use functionality of the base class without having two basically identical foreach loops one after the other.

I can’t copy the lists to another list or something of the sort, as I need to use the lists in their original form separately after the operation is complete.

Is there a way to do this without writing a function?

class Program
{
    static void Main(string[] args)
    {
        // I have two lists of inherited classes
        List<Babby1> list1 = returnBabby1();
        List<Babby2> list2 = returnBabby2();

        // I want to iterate through both, and do the same thing, which is a part
        // of the base class functionality.
        // Basically I want this to be a single foreach loop.
        foreach (Babby1 item in list1)
            item.var = 50;

        foreach (Babby2 item in list2)
            item.var = 50;

        // I have to send them as separate lists, the type being the original (inherited) class
        sendBabby1(list1);
        sendBabby2(list2);
    }

    static void sendBabby1(List<Babby1> list)
    {
    }

    static void sendBabby2(List<Babby2> list)
    {
    }

    static List<Babby1> returnBabby1()
    {
        return new List<Babby1>();
    }

    static List<Babby2> returnBabby2()
    {
        return new List<Babby2>();
    }
}

class Base
{
    public int var;
}

class Babby1 : Base
{
    public int var1;
}

class Babby2 : Base
{
    public int var2;
}

Answer 1

This should do the trick…

foreach (var item in list1.Concat<Base>(list2))
{
    // Do your thing
}

EDIT: I changed Union to Concat as I think that it’s probably more appropriate.