CS1061, CS0117: `System.Linq.Enumerable' does not contain a definition for `Zip'

Question

I'm using Unity3D, Mono, C# on Mac OSX 10.8. I'm trying to use .Net Enumerable.Zip. But copy-pasting the MSDN example gives me a cs0117 error.

Minimal not working example:

using UnityEngine;
using System.Collections;
using System.Linq;

public class Asteroids : MonoBehaviour {
void Start () { 
    int[] numbers = { 1, 2, 3, 4 };
    string[] words = { "one", "two", "three" };
    var numbersAndWords = numbers.Zip(words, (first, second) => first + " " + second);
}   
}

Error Message:

error CS1061: Type int[]' does not contain a definition forZip' and no extension method Zip' of typeint[]' could be found (are you missing a using directive or an assembly reference?)

I tried replacing "numbers.Zip" with "Enumerable.Zip", then I got this:

error CS0117: System.Linq.Enumerable' does not contain a definition forZip'

Why did these happend?

Answer 1

Given @SLaks' answer, it's easy to roll your own Zip:

public static IEnumerable<TResult> Zip<TA, TB, TResult>(
    this IEnumerable<TA> seqA, IEnumerable<TB> seqB, Func<TA, TB, TResult> func)
{
    if (seqA == null) throw new ArgumentNullException("seqA");
    if (seqB == null) throw new ArgumentNullException("seqB");

    using (var iteratorA = seqA.GetEnumerator())
    using (var iteratorB = seqB.GetEnumerator())
    {
        while (iteratorA.MoveNext() && iteratorB.MoveNext())
        {
            yield return func(iteratorA.Current, iteratorB.Current);
        }
    }
}