How does a Binding actually work?

I've been learning WPF for a few months now and I'm curious 开发者_StackOverflowabout one thing. How does a Binding actually work? I mean, what happends, under the hood. I don't expect that anyone here would give a detailed explanation but maybe a good resource or link where to read up on something like this. I've been searching and googling for this but no good hits so far.

I realize that to fully understand this you would probably have to understand most parts of the framework but a little basic understanding would be great.

Thanks

There are two aspects to consider in binding, getting values in to the UI and having the UI be notified of changes in its DataContext.

Basically you can bind almost anything to any POCO object, the object does not need to implement anything special. The restriction with plain objects is the binding target will not be told when the underlying value changes.

Property changes are propogated through one of three mechanisims:

Dependancy Properties : will notify the binding system when its value changes, can also be used for animations.

INotifyPropertyChanged : If the binding is to a property on an object which implements INotifyPropertyChanged, the binding system will look for subscribe to the PropertyChanged event and update the binding target, when this event is raised, property names are sent as Strings.

*Property*Changed events : The last thing bindings will look for is an event with a name the same as the source property and Changed on the end, so a Name property would need to have a public event called NameChanged, this allows WPF to bind to older .net classes such as 1.1.

I don't know much about the specifics of binding in WPF, but if it's the same principle behind binding in System.ComponentModel and Windows Forms, then a blog article I wrote recently might help to shed some light on it for you:

Some Background on Windows Forms Data Binding

Basically, binding sources have to implement IList, IListSource, ITypedList or IBindingList. Through either reflection or explicit definition, data sources expose PropertyDescriptor objects which describe their bindable properties. The names of these properties (which may or may not be the names of actual properties on the objects contained in the data source - e.g. in DataTable, they are column names instead) are matched against the DisplayMember/ValueMember property or, in the case of WPF, the binding path.

This is quite a difficult question to answer. I believe there are roughly two aspects to an answer. The first is the documentation. If you go through all the documentation of binding expressions, including how paths are build and e.g. the helper classes like BindingOperations, you can find out a lot. If that's not enough, you can always dive into the code by downloading it from the Microsoft Source Initiative site.