ICollection<T>.Add(T) - Performance Test, C#

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Diagnostics;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text.RegularExpressions;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            //Your code goes here
            var collection = new List<Guid>();
            for(var i = 0; i<100000; i++){
               collection.Add(Guid.NewGuid());
            }
            
            string listTime = TestAddSpeed(collection, new List<Guid>());
            string hashTime = TestAddSpeed(collection, new HashSet<Guid>());
            string collTime = TestAddSpeed(collection, new Collection<Guid>());
            string ssTime = TestAddSpeed(collection, new SortedSet<Guid>());
            string llTime = TestAddSpeed(collection, new LinkedList<Guid>());
            string arrayTime = TestNewArray(collection);
                
            Console.WriteLine(string.Format("Hash:       {0}", hashTime));
            Console.WriteLine(string.Format("List:       {0}", listTime));
            Console.WriteLine(string.Format("Collection: {0}", collTime));
            Console.WriteLine(string.Format("SortedSet:  {0}", ssTime));
            Console.WriteLine(string.Format("LinkedList: {0}", llTime));
            Console.WriteLine(string.Format("Array:      {0}", arrayTime));
        }
        
        private static string TestNewArray(IList<Guid> collection)
        {
            var stopwatch = new Stopwatch();
            stopwatch.Start();
            var arr = new Guid[collection.Count];
            for(var i = 0; i< collection.Count-1; i++)
            {
                arr[i] = collection[i];
            } 
            stopwatch.Stop();
            return stopwatch.Elapsed.ToString();
        }
        
        private static string TestAddSpeed<T>(IList<Guid> collection, T run) where T:ICollection<Guid>
        {
            var stopwatch = new Stopwatch();
            stopwatch.Start();
            for(var i = 0; i < collection.Count-1; i++){
                run.Add(collection[i]);
            }
            stopwatch.Stop();
            run.Clear();
            run = default(T);
            return stopwatch.Elapsed.ToString();
        }
    }
}

Show compiler warnings [ + ] Show input
Compilation time: 0,17 sec, absolute running time: 0,28 sec, cpu time: 0,28 sec, average memory usage: 32 Mb, average nr of threads: 5