INotifyPropertyChanged的：是[CallerMemberName]相比会更慢的替代品？ [英] INotifyPropertyChanged : is [CallerMemberName] slow compared to alternatives?

问题描述

有像这个，对实施提出不同的方法 INotifyPropertyChanged的。

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

考虑followng基本实现：

Consider the followng basic implementation :

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
            }
        }
    }
}

我想这一个来取代它：

I'd like to replace it with this one :

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();
            }
        }
    }
}

但有时候我读到相比，替代品 [CallerMemberName] 属性有表现不佳。真的是这样，为什么？是否使用反射？

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

没有，使用 [CallerMemberName] 不是慢比上基本实现。

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

这是因为，根据这个MSDN页面

来电信息值发出为文字到中间
  在编译时语言（IL）

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

我们可以检查与任何反汇编白细胞介素（如 ILSpy ）：在code的属性中的设置操作编译完全相同的方式：

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​​，没有使用反射在这里。

So no use of Reflection here.

（样品与VS2013编译）

(sample compiled with VS2013)

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