Implementing INotifyPropertyChanged - does a better way exist?

Question

Microsoft should have implemented something snappy for INotifyPropertyChanged, like in the automatic properties, just specify {get; set; notify;} I

Answer 1

Without using something like postsharp, the minimal version I use uses something like:

public class Data : INotifyPropertyChanged
{
    // boiler-plate
    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
    }
    protected bool SetField(ref T field, T value, string propertyName)
    {
        if (EqualityComparer.Default.Equals(field, value)) return false;
        field = value;
        OnPropertyChanged(propertyName);
        return true;
    }

    // props
    private string name;
    public string Name
    {
        get { return name; }
        set { SetField(ref name, value, "Name"); }
    }
}

Each property is then just something like:

private string name;
public string Name
{
    get { return name; }
    set { SetField(ref name, value, "Name"); }
}

which isn't huge; it can also be used as a base-class if you want. The bool return from SetField tells you if it was a no-op, in case you want to apply other logic.

---

or even easier with C# 5:

protected bool SetField(ref T field, T value,
    [CallerMemberName] string propertyName = null)
{...}

which can be called like this:

set { SetField(ref name, value); }

with which the compiler will add the "Name" automatically.

---

C# 6.0 makes the implementation easier:

protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}

---

...and now with C#7:

protected void OnPropertyChanged(string propertyName)
   => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));

protected bool SetField(ref T field, T value,[CallerMemberName] string propertyName =  null)
{
    if (EqualityComparer.Default.Equals(field, value)) return false;
    field = value;
    OnPropertyChanged(propertyName);
    return true;
}

private string name;
public string Name
{
    get => name;
    set => SetField(ref name, value);
}

---

And, with C# 8 and Nullable reference types, it would look like this:

public event PropertyChangedEventHandler? PropertyChanged;

protected void OnPropertyChanged(string? propertyName) => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));

protected bool SetField(ref T field, T value, [CallerMemberName] string? propertyName = null)
{
    if (EqualityComparer.Default.Equals(field, value)) return false;
    field = value;
    OnPropertyChanged(propertyName);
    return true;
}

private string name;
public string Name
{
    get => name;
    set => SetField(ref name, value);
}