与实现INotifyPropertyChanged时的替代方法相比，[CallerMemberName]是否较慢？ [英] Is [CallerMemberName] slow compared to alternatives when implementing INotifyPropertyChanged?

问题描述

好文章建议实现的不同方法INotifyPropertyChanged 。

There are good articles that suggest different ways for implementing INotifyPropertyChanged.

请考虑以下基本实现：

class BasicClass : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    private void FirePropertyChanged(string propertyName)
    {
        var handler = PropertyChanged;
        if (handler != null)
            handler(this, new PropertyChangedEventArgs(propertyName));
    }

    private int sampleIntField;

    public int SampleIntProperty
    {
        get { return sampleIntField; }
        set
        {
            if (value != sampleIntField)
            {
                sampleIntField = value;
                FirePropertyChanged("SampleIntProperty"); // ouch ! magic string here
            }
        }
    }
}

我想用这个替换它：

using System.Runtime.CompilerServices;

class BetterClass : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    // Check the attribute in the following line :
    private void FirePropertyChanged([CallerMemberName] string propertyName = null)
    {
        var handler = PropertyChanged;
        if (handler != null)
            handler(this, new PropertyChangedEventArgs(propertyName));
    }

    private int sampleIntField;

    public int SampleIntProperty
    {
        get { return sampleIntField; }
        set
        {
            if (value != sampleIntField)
            {
                sampleIntField = value;
                // no "magic string" in the following line :
                FirePropertyChanged();
            }
        }
    }
}

但是有时我读到 [CallerMemberName] 属性与替代方法相比性能较差。那是真的，为什么？

But sometimes I read that the [CallerMemberName] attribute has poor performances compared to alternatives. Is that true and why? Does it use reflection?

推荐答案

不，使用 [CallerMemberName] 并不比最基本的实现慢。

No, the use of [CallerMemberName] is not slower than the upper basic implementation.

这是因为，根据此MSDN页面，

呼叫者信息值在编译时作为文字发送到中间
语言（IL）

Caller Info values are emitted as literals into the Intermediate Language (IL) at compile time

我们可以使用任何IL反汇编程序（例如 ILSpy ）检查该属性的 SET操作的代码是否已编译完全相同：

We can check that with any IL disassembler (like ILSpy) : the code for the "SET" operation of the property is compiled exactly the same way :

因此在这里不使用反射。

So no use of Reflection here.

（使用VS2013编译的示例）

(sample compiled with VS2013)

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