ForeachTest.cs

using UnityEngine;
using System.Collections.Generic;

public class ForeachTest : MonoBehaviour
{
    private string _testString = "this is a test";
    private List<string> _testList;
    private const int _numIterations = 10000;

    void Start()
    {
        _testList = new List<string>();
        for (int i = 0; i < _numIterations; ++i)
        {
            _testList.Add(_testString);
        }
    }

    void Update()
    {
        Profiler.BeginSample("ForeachIter");
        ForeachIter();
        Profiler.EndSample();
        Profiler.BeginSample("WhileIter");
        WhileIter();
        Profiler.EndSample();
        Profiler.BeginSample("ForLoop");
        ForLoop();
        Profiler.EndSample();
    }

    private void ForeachIter()
    {
        string s;

        for (int i = 0; i < 1000; ++i)
        {
            foreach (string str in _testList)
            {
                s = str;
            }
        }
    }

    private void ForLoop()
    {
        string s;

        for (int i = 0; i < 1000; ++i)
        {
            for (int index = 0; index < _testList.Count; index++)
            {
                string str = _testList[index];
                s = str;
            }
        }
    }

    private void WhileIter()
    {
        string s;
        string item;

        for (int i = 0; i < 1000; ++i)
        {
            var enumerator = _testList.GetEnumerator();

            while (enumerator.MoveNext())
            {
                item = enumerator.Current;
                s = item;
            }
        }
    }

}