NotifyPropertyChanged - kswoll/someta GitHub Wiki

Hey, you could of course use PropertyChanged.Fody (and you probably should! it offers a number of great features and is well maintained). That said, we think it's also a good example of the power you have at your fingertips with Someta.

So let's define the attribute:

public class NotifyPropertyChangedAttribute : Attribute, IPropertySetInterceptor, IClassEnhancer
{
    [InjectAccess("OnPropertyChanged")]
    public Action<object, string, object, object> OnPropertyChanged { get; set; }

    public void SetPropertyValue(PropertyInfo propertyInfo, object instance, object oldValue,
        object newValue, Action<object> setter)
    {
        if (!Equals(oldValue, newValue))
        {
            setter(newValue);
            OnPropertyChanged(instance, propertyInfo.Name, oldValue, newValue);
        }
    }
}

Now a sample base class that you would subclass to opt in to INotifyPropertyChanged behavior:

[NotifyPropertyChanged]
public class BaseClass : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName, object oldValue, object newValue)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

Finally, a sample subclass:

public class TestClass : BaseClass
{
    public string StringProperty { get; set; }
}

That's it! To elaborate, the attribute implements both IPropertySetInterceptor and IClassEnhancer. It implements IPropertySetInterceptor which defines the SetPropertyValue method. It also declares a property of a delegate type that matches the signature of the OnPropertyChanged method, except it also introduces a new parameter at the front to accomodate the instance. It uses the InjectAccess attribute to identify the method in your base class that will be called when the property value changes. (Note: if your method has overloads, you should provide an InjectTarget attribute on your OnPropertyChanged method to link the method to the injected accessor.)