Wpf binding not updating property

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One of the central idioms of WPF development is having presentation tier classes implement the INotify Property Changed interface.

Anybody who has done more than a “Hello World” WPF application or two is almost certainly familiar with this and quite probably knows it like the back of his or her hand.

After being shown this technique and using it for a while, I felt increasingly like something wasn’t quite right and there was room for improvement. First, the property changed args were being created at application startup, for every property, whether or not anyone ever set it.

Pedantically (though sometimes practically), this is not as efficient as it could be.

Instead, there’s a static object initialized at application startup.

You pay a one-time cost at startup, and then everything is much more efficient after that.

The tradeoff is probably worth it if you have a high ratio of model modification to model creation. If you’re like me, the presence of “Text” everywhere in this set of examples has been like a little pebble stuck in your shoe.

It’s annoying enough to irritate, but not necessarily quite annoying enough to fix at the moment.

Instead of in our setter, it sits above our property.

To counter those two issues, I added a base class from which models (and View Models, if they expose properties directly) should inherit.

If you don’t like a common ancestor like that, you could always implement this with an interface and a default behavior extension method on that interface, but I’m not a fan of extension methods for ‘extending’ your own code in your own assembly (extension methods just being syntactic sugar on free-floating static methods) What’s going on here is that we maintain a cache of Event Args.

As I’ve been learning WPF with C# over the past year (coming from a background of C and Java before that), my implementation of this has evolved a bit, and I thought I’d share the progression and my thoughts on why each subsequent implementation is an improvement.

By way of background, for anyone not familiar or looking for a refresher, this interface allows XAML bindings to keep in sync with the C# class.

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