How do you get the index of the current iteration of a foreach loop?

Question

Is there some rare language construct I haven\'t encountered (like the few I\'ve learned recently, some on Stack Overflow) in C# to get a value representing the current iter

Answer 1

You could wrap the original enumerator with another that does contain the index information.

foreach (var item in ForEachHelper.WithIndex(collection))
{
    Console.Write("Index=" + item.Index);
    Console.Write(";Value= " + item.Value);
    Console.Write(";IsLast=" + item.IsLast);
    Console.WriteLine();
}

Here is the code for the ForEachHelper class.

public static class ForEachHelper
{
    public sealed class Item
    {
        public int Index { get; set; }
        public T Value { get; set; }
        public bool IsLast { get; set; }
    }

    public static IEnumerable> WithIndex(IEnumerable enumerable)
    {
        Item item = null;
        foreach (T value in enumerable)
        {
            Item next = new Item();
            next.Index = 0;
            next.Value = value;
            next.IsLast = false;
            if (item != null)
            {
                next.Index = item.Index + 1;
                yield return item;
            }
            item = next;
        }
        if (item != null)
        {
            item.IsLast = true;
            yield return item;
        }            
    }
}