Is there any benefit of using the nameof operator instead of the CallerMemberNameAttribute to notify property changes in .NET 4.5.3?

Question

With the advent of .NET 4.5.3, WPF developers now have three (or more) ways to notify the INotifyPropertyChanged Interface of property changes. Basically, my question is Which of the two methods introduced from.NET 4.5 onwards is the more efficient way to notify property changes and whether either way has any benefit when being used in WPF?

Background

For those not so familiar with this subject, here are the main three methods. The first is the original, more error prone method of simply passing a string:

public string TestValue
{
    get { return testValue; }
    set { testValue = value; NotifyPropertyChanged("TestValue"); }
}

protected virtual void NotifyPropertyChanged(string propertyName)
{
    if (PropertyChanged != null)
    {
        PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}

The second method was introduced in .NET 4.5; the CallerMemberNameAttribute:

public string TestValue
{
    get { return testValue; }
    set { testValue = value; NotifyPropertyChanged(); }
}

protected virtual void NotifyPropertyChanged([CallerMemberName]string propertyName = "")
{
    if (PropertyChanged != null)
    {
        PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}

The third and most recent method was (or will soon be) introduced in C#6.0 as part of .NET 4.5.3; the nameof Operator:

public string TestValue
{
    get { return testValue; }
    set { testValue = value; NotifyPropertyChanged(nameof(TestValue)); }
}

protected virtual void NotifyPropertyChanged(string propertyName)
{
    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}

My own assumption would be that the original, more error prone method of simply passing a string would be the most efficient, as I can only imagine that the other two methods use some form of reflection. However, I'm really keen to find out which of the other two methods is more efficient and whether there would actually be any difference between using the CallerMemberNameAttribute attribute and the nameof operator in a WPF context.

Answer 1

About efficiency: using a string directly, CallerMemberNameAttribute, nameof are all exactly the same since the string is injected by the compiler at compile-time. There's no reflection involved.

We can see that using TryRoslyn that produces this for CallerMemberNameAttribute:

public string TestValue
{
    get { return this.testValue; }
    set { this.testValue = value; this.NotifyPropertyChanged("TestValue"); }
}
protected virtual void NotifyPropertyChanged([CallerMemberName] string propertyName = "")
{
    if (this.PropertyChanged != null)
    {
        this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}

And this for nameof:

public string TestValue
{
    get { return this.testValue; }
    set { this.testValue = value; this.NotifyPropertyChanged("TestValue"); }
}
protected virtual void NotifyPropertyChanged(string propertyName)
{
    if (this.PropertyChanged != null)
    {
        this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}

Since at runtime all options are simply a string there's no problem with the WPF context.

About convenience: CallerMemberNameAttribute requires you to have an optional parameter while nameof doesn't but nameof requires you to specify the property while CallerMemberNameAttribute doesn't.

I predict that nameof would turn out to be so popular that it would be much simpler to use it instead.

Answer 2

The CallerMemberNameAttribute can only be used on the called function the get the name of the caller function.

The nameof operator goes way beyond that. It can be used anywhere.

If you want to reason about it just in the scope of WPF data binding, take this example:

public string FullName
{
   get
   {
       return string.Format(
           "{0} {1}",
           this.firstName,
           this.lastName);
   }
}

public string FirstName
{
   get
   {
       return this.firstName;
   }
   set
   {
       if (value != this.firstName)
       {
           this.firstName = value;
           NotifyPropertyChanged(nameof(FirstName));
           NotifyPropertyChanged(nameof(FullName));
        }
   }
}

public string LasttName
{
   get
   {
       return this.lastName;
   }
   set
   {
       if (value != this.lastName)
       {
           this.lastName = value;
           NotifyPropertyChanged(nameof(LasttName));
           NotifyPropertyChanged(nameof(FullName));
        }
   }
}