Yield_Versus_Linq_Tests.cs

Yield_Versus_Linq_Tests.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using NUnit.Framework;

[TestFixture]
public class Yield_Versus_Linq_Tests
{
        [Test]
        public void Yield_Is_Slower_Than_Select()
        {
            var numbers = Enumerable.Range(1, 1000000);

            var yieldElapsed = GetElapsed(numbers, GetYieldCalculations);
            var selectElapsed = GetElapsed(numbers, GetSelectCalculations);

            Assert.IsTrue(yieldElapsed > selectElapsed);
        }

        private static TimeSpan GetElapsed(IEnumerable<int> numbers, Func<IEnumerable<int>, IEnumerable<double>> operation)
        {
            var timer = new Stopwatch();
            timer.Start();
            var results = operation(numbers).ToList();
            timer.Stop();
            return timer.Elapsed;
        }

        private static IEnumerable<double> GetYieldCalculations(IEnumerable<int> numbers)
        {
            foreach (var number in numbers)
            {
                yield return Math.Sqrt(number);
            }
        }

        private static IEnumerable<double> GetSelectCalculations(IEnumerable<int> numbers)
        {
            return numbers.Select(number => Math.Sqrt(number));
        }
}