c# - lambda 表达式或 get_property 函数在 C# 中的实际作用是什么？

Question

public class People
{
    private string _name;
    public string Name { get; set; }

    public string SName;

    public string LamName => _name;
    public People(string s)
    {
        _name = s;
        Name = s;
    }

    public string GetName1()
    {
        return _name;
    }

    public string GetName2()
    {
        return Name;
    }

    public void OnlyFunc()
    {
        
    }
}

class Program
{
    int interCount = 100000000;

    public void AsAttribute()
    {
        People people = new People("Wave");
        Stopwatch stopwatch = Stopwatch.StartNew();
        for (int i = 0; i < interCount; ++i)
        {
            object val = people.SName;
        }
        stopwatch.Stop();
        Console.WriteLine("AsAttribute: {0}ms", stopwatch.ElapsedMilliseconds);
    }

    public void Directly()
    {
        People people = new People("Wave");
        Stopwatch stopwatch = Stopwatch.StartNew();
        for (int i = 0; i < interCount; i++)
        {
            object value = people.Name;
        }
        stopwatch.Stop();

        Console.WriteLine("Directly: {0}ms", stopwatch.ElapsedMilliseconds);
    }

    public void UseFunc1()
    {
        People people = new People("Wave");
        Stopwatch stopwatch = Stopwatch.StartNew();
        for (int i = 0; i < interCount; i++)
        {
            object value = people.GetName1();
        }
        stopwatch.Stop();

        Console.WriteLine("UseFunc1: {0}ms", stopwatch.ElapsedMilliseconds);
    }

    public void UseFunc2()
    {
        People people = new People("Wave");
        Stopwatch stopwatch = Stopwatch.StartNew();
        for (int i = 0; i < interCount; i++)
        {
            object value = people.GetName2();
        }
        stopwatch.Stop();

        Console.WriteLine("UseFunc2: {0}ms", stopwatch.ElapsedMilliseconds);
    }

    public void Lambda()
    {
        People people = new People("Wave");
        Stopwatch stopwatch = Stopwatch.StartNew();
        for (int i = 0; i < interCount; i++)
        {
            object value = people.LamName;
        }
        stopwatch.Stop();

        Console.WriteLine("Lambda: {0}ms", stopwatch.ElapsedMilliseconds);
    }

    static void Main(string[] args)
    {
        Program p = new Program();
        p.AsAttribute();
        p.Directly();
        p.Lambda();
        p.UseFunc1();
        p.UseFunc2();
    }
}

这是我测试的例子，我得到的时间成本结果如下:

AsAttribute: 82ms
Directly: 213ms
Lambda: 229ms
UseFunc1: 255ms
UseFunc2: 418ms

我想知道是什么导致了差异，当我将其标记为属性时，它获得最佳性能，当我使用 lambda 表达式或函数获取属性时，性能下降。

Answer 1

从代码中可以看出第一次运行是现场运行，而不是属性。(所以是最快的，看IL上的代码就知道了)而direct就是对属性的直接执行。Lambda 表达式等同于 get {return ...} ，因此与 Directly 没有区别。UseFunc1 通过调用该方法很慢。UseFunc2 是最慢的，因为它执行两个步骤，如 mehtod --> property。

这是关于您的 C# 代码的 il 代码

私有(private)字符串_name;

[CompilerGenerated]
[DebuggerBrowsable(DebuggerBrowsableState.Never)]
private string <Name>k__BackingField;

public string SName;

public string Name
{
    [CompilerGenerated]
    get
    {
        return <Name>k__BackingField;
    }
    [CompilerGenerated]
    set
    {
        <Name>k__BackingField = value;
    }
}

public string LamName
{
    get
    {
        return _name;
    }
}

public People(string s)
{
    _name = s;
    Name = s;
}

public string GetName1()
{
    return _name;
}

public string GetName2()
{
    return Name;
}