Neat way to write loop that has special logic for the first item in a collection

Question

Often I have to code a loop that needs a special case for the first item, the code never seems as clear as it should ideally be.

Short of a redesign of the C# language,

Answer 1

Both of those are perfectly acceptable algorithms for processing the first element differently, and there really isn't a different way to do it. If this pattern is repeated a lot, you could hide it behind an overload of ForEach():

public static void ForEach(this IEnumerable elements, Action firstElementAction, Action standardAction)
{
    var firstItem = true;
    foreach(T element in elements)
    {
        if(firstItem)
        {
            firstItem = false;
            firstElementAction(element)
        }
        else
            standardAction(element)
    }
}

...

//usage
yyy.ForEach(t=>(other code when first item), t=>(normal processing code));

Linq makes it a little cleaner:

PerformActionOnFirstElement(yyy.FirstOrDefault());
yyy.Skip(1).ForEach(x=>(normal processing code));