Checking out Jouni Heikniemi’s excellent map of What’s new in .NET 4.5 I spotted this comment:

Methods can access call site info as parameter (CallerInfo)

Intrigued, some google-fu revealed that Anders Hejlberg demoed this in his session at build - new attributes [CallerFilePath], [CallerLineNumber] and [CallerMemberName], available for use on method parameters and automatically filled in by the compiler.

The immediate use that springs to mind is for the implementation of the INotifyPropertyChanged interface:

public string Name
{
    get { return mName; }
    set {
        if (!Equals(mName, value)) {
            mName = value;
            OnNotifyPropertyChanged();
        }
    }
}

protected void OnNotifyPropertyChanged(
    [CallerMemberName] string propertyName = "")
{
    ... 
}

Note how we no longer need to pass the name of the property as a magic string to OnNotifyPropertyChanged() because the compiler will fill it in for us.

I’m sure there’ll be more inventive uses though …

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