Question

In this code I noticed the .Notify method is an extension method. Why and what is the code behind this method?

public class Notifier : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    (...)

    public void NotifyPropertyChanged(Expression<Func<object>> property)
    {
        this.PropertyChanged.Notify(property);
    }
}

Answer 1

This extension method isn’t provided by the .NET framework. Therefore, it is a custom extension method created somewhere in your code. To know what exactly it does, navigate to it and look at the source code (F12).

Generally speaking, I assume it will raise the PropertyChanged event with the property name extracted from the expression that is passed to it.