how do I check if an entity is the first element of a foreach loop

There are several ways that you could do that.

1. Use a for loop instead
2. Set a Boolean flag
3. Use Linq to get the list.First() and then foreach over list.Skip(1)

I like the Linq way, but without the Skip(1), this way you can also use it for the last item in a list and your code remains clean imho :)

foreach(var item in items)
{
    if (items.First()==item)
        item.firstStuff();

    else if (items.Last() == item)
        item.lastStuff();

    item.otherStuff();
}