通过设置对象的初始化与否属性：有什么区别？ [英] Setting properties via object initialization or not : Any difference ?

问题描述

下面是一个简单的问题：是有这之间的任何（性能）​​的区别：

Here's a simple question : Is there any (performance) difference between this :

Person person = new Person()
{
  Name = "Philippe",
  Mail = "[e-mail]",
};

这

and this

Person person = new Person();
person.Name = "Philippe";
person.Mail = "[e-mail]";

您能想象更多的性能更大的对象。

You can imagine bigger object with more properties.

推荐答案

他们除了几乎完全等同第一种方法（使用的对象初始化）只能在C＃3.0和更高版本。任何性能上的差异仅仅是轻微的，不值得担心。

They are almost exactly equivalent except that the first method (using an object initializer) only works in C# 3.0 and newer. Any performance difference is only minor and not worth worrying about.

他们生产的几乎相同的IL代码。首先给出了这样的：

They produce almost identical IL code. The first gives this:

.method private hidebysig instance void ObjectInitializer() cil managed
{
    .maxstack 2
    .locals init (
        [0] class Person person,
        [1] class Person <>g__initLocal0)
    L_0000: newobj instance void Person::.ctor()
    L_0005: stloc.1 
    L_0006: ldloc.1 
    L_0007: ldstr "Philippe"
    L_000c: callvirt instance void Person::set_Name(string)
    L_0011: ldloc.1 
    L_0012: ldstr "[e-mail]"
    L_0017: callvirt instance void Person::set_Mail(string)
    L_001c: ldloc.1 
    L_001d: stloc.0 
    L_001e: ldloc.0 
    L_001f: callvirt instance string [mscorlib]System.Object::ToString()
    L_0024: pop 
    L_0025: ret 
}

第二给出了这样的：

.method private hidebysig instance void SetProperties() cil managed
{
    .maxstack 2
    .locals init (
        [0] class Person person)
    L_0000: newobj instance void Person::.ctor()
    L_0005: stloc.0 
    L_0006: ldloc.0 
    L_0007: ldstr "Philippe"
    L_000c: callvirt instance void Person::set_Name(string)
    L_0011: ldloc.0 
    L_0012: ldstr "[e-mail]"
    L_0017: callvirt instance void Person::set_Mail(string)
    L_001c: ldloc.0 
    L_001d: callvirt instance string [mscorlib]System.Object::ToString()
    L_0022: pop 
    L_0023: ret 
}

正如你所看到的，会产生几乎相同的代码。 。请参见下面的确切C＃代码我编译

As you can see, nearly identical code is generated. See below for the exact C# code I compiled.

性能测量表明一个非常小的性能提升非常相似的结果为使用对象初始化语法：

Performance measurements show very similar results with a very small performance improvement for using the object initializer syntax:

Method               Iterations per second
ObjectInitializer    8.8 million
SetProperties        8.6 million

代码我用来测试性能：

using System;

class Person
{
    public string Name { get; set; }
    public string Mail { get; set; }
}

class Program
{
    private void ObjectInitializer()
    {
        Person person = new Person()
        {
            Name = "Philippe",
            Mail = "[e-mail]",
        };
        person.ToString();
    }

    private void SetProperties()
    {
        Person person = new Person();
        person.Name = "Philippe";
        person.Mail = "[e-mail]";
        person.ToString();
    }

    private const int repetitions = 100000000;

    private void Time(Action action)
    {
        DateTime start = DateTime.UtcNow;
        for (int i = 0; i < repetitions; ++i)
        {
            action();
        }
        DateTime end = DateTime.UtcNow;
        Console.WriteLine(repetitions / (end - start).TotalSeconds);
    }

    private void Run()
    {
        Time(ObjectInitializer);
        Time(SetProperties);
        Console.WriteLine("Finished");
        Console.ReadLine();
    }

    private static void Main()
    {
        new Program().Run();
    }
}

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