Mike-Ward.Net

Implementing INotifyPropertyChanged

Writing programs in WPF usually involves implementing INotifyPropertyChanged. Implementing this interface the standard way involves a fair-bit of boilerplate code. It’s tiresome and error prone.

There are many ways to mitigate this issue. Frameworks like Caliburn.Micro or post compilers like PostSharp can reduce the amount of required boilerplate.

I opt for a middle ground and implement the interface directly with the addition of one helper method.

public event PropertyChangedEventHandler PropertyChanged;

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

private void Set<T>(ref T property, T value, [CallerMemberName] string propertyName = null)
{
    if (EqualityComparer<T>.Default.Equals(property, value)) return;
    property = value;
    OnPropertyChanged(propertyName);
}

I can then write properties as follows

public string Name
{
    get { return _name; }
    set { Set(ref _name, value); }
}

It’s a compromise between a big hammer like Caliburn.Micro or PostSharp and boilerplate.

The EqualityComparer<T>.Default.Equals(property, value) call avoids boxing value types, a common criticism of some approaches.