Looping through 2 Lists at once

Question

I have two lists that are of the same length, is it possible to loop through these two lists at once?

I am looking for the correct syntax to do the below

Answer 1

[edit]: to clarify; this is useful in the generic LINQ / IEnumerable context, where you can't use an indexer, because a: it doesn't exist on an enumerable, and b: you can't guarantee that you can read the data more than once. Since the OP mentions lambdas, it occurs that LINQ might not be too far away (and yes, I do realise that LINQ and lambdas are not quite the same thing).

It sounds like you need the missing Zip operator; you can spoof it:

static void Main()
{
    int[] left = { 1, 2, 3, 4, 5 };
    string[] right = { "abc", "def", "ghi", "jkl", "mno" };

    // using KeyValuePair<,> approach
    foreach (var item in left.Zip(right))
    {
        Console.WriteLine("{0}/{1}", item.Key, item.Value);
    }

    // using projection approach
    foreach (string item in left.Zip(right,
        (x,y) => string.Format("{0}/{1}", x, y)))
    {
        Console.WriteLine(item);
    }
}

// library code; written once and stuffed away in a util assembly...

// returns each pais as a KeyValuePair<,>
static IEnumerable> Zip(
    this IEnumerable left, IEnumerable right)
{
    return Zip(left, right, (x, y) => new KeyValuePair(x, y));
}

// accepts a projection from the caller for each pair
static IEnumerable Zip(
    this IEnumerable left, IEnumerable right,
    Func selector)
{
    using(IEnumerator leftE = left.GetEnumerator())
    using (IEnumerator rightE = right.GetEnumerator())
    {
        while (leftE.MoveNext() && rightE.MoveNext())
        {
            yield return selector(leftE.Current, rightE.Current);
        }
    }
}