将数据添加到集合中，哪个效率更高？

Question

I am adding data to a collection, but I don't know which is more efficient.

Using a foreach loop,

internal class CollectionClass
{
    public List<string> ListData { get; set; }

    public CollectionClass()
    {
        ListData = new List<string>();
        string[] names = { "Matt", "Joanne", "Robert" };
        foreach (var item in names)
        {
            ListData.Add(item);
        }
    }
}

Or is this more efficent?

internal class CollectionClass
{
    public List<string> ListData { get; set; }

    public CollectionClass()
    {           
        ListData.Add("Matt");
        ListData.Add("Joanne");
        ListData.Add("Robert");
    }
 }

All logic suggests the latter, but with big data is this the case?

Answer 1

There is no big difference unless you're adding like millions of entries, so select the code that you're more comfortable with.

Here is a benchmark of 4 different ways.

1) Array with loop (as in your first method).

2) Array with AddRange . Almost identical, but code is a bit nicer.

3) Using Add (as in your second method).

4) Using list initializer.

Sadly I cannot run each test more than 10,000 times because the dotnetfiddle.net gives a memory error, but you can copy the code and try it on your computer with higher number like 100,000. Anyway, the result is 1 and 2 are almost identical and faster than 3 and 4 which are very close. But you can see clearly how little the differences are even at 10,000 times of inserting 3 items. So it's really negligible.

Link to fiddle demo

Test Results (in milliseconds):

Test1: 6

Test2: 6

Test3: 2

Test4: 2

Test code:

using System;
using System.Collections.Generic;

public class Program
{
    public static void Main()
    {
        var c = new CollectionClass();
        var watch = System.Diagnostics.Stopwatch.StartNew();
        for (var i = 0; i < 10000; i++)
            c.Test1();
        watch.Stop();
        Console.WriteLine("Test1:" + watch.ElapsedMilliseconds);

        watch = System.Diagnostics.Stopwatch.StartNew();
        for (var i = 0; i < 10000; i++)
            c.Test2();
        watch.Stop();
        Console.WriteLine("Test2:" + watch.ElapsedMilliseconds);

        watch = System.Diagnostics.Stopwatch.StartNew();
        for (var i = 0; i < 10000; i++)
            c.Test3();
        watch.Stop();
        Console.WriteLine("Test3:" + watch.ElapsedMilliseconds);

        watch = System.Diagnostics.Stopwatch.StartNew();
        for (var i = 0; i < 10000; i++)
            c.Test4();
        watch.Stop();
        Console.WriteLine("Test4:" + watch.ElapsedMilliseconds);
    }
}

internal class CollectionClass
{
    public List<string> ListData { get; set; }

    public void Test1()
    {
        ListData = new List<string>();
        string[] names = { "Matt", "Joanne", "Robert" };

        foreach (var item in names)
            ListData.Add(item);
    }

    public void Test2()
    {
        string[] names = { "Matt", "Joanne", "Robert" };
        ListData = new List<string>();
        ListData.AddRange(names);
    }

    public void Test3()
    {
        ListData = new List<string>();
        ListData.Add("Matt");
        ListData.Add("Joanne");
        ListData.Add("Robert");
    }

    public void Test4()
    {
        ListData = new List<string>(){ "Matt", "Joanne", "Robert" };
    }
}