Bindings

By default, all XAML technologies support binding out of the box. However other platforms (such as Xamarin.Android and Xamarin.iOS) don’t. Catel provides a binding system for these platforms, which is described in this topic.

Note that although the binding system in Catel is very powerful, it will never be as flexible / powerful as the native XAML binding system. We do try to support as many features as possible though.

For examples, check out the following pages:

Binding system explained

The binding system consists of several classes. Below is an architectural overview.

As the image shows, each view will have their own BindingContext. A BindingContext contains all the bindings currently available in the view and allows adding / removing bindings dynamically when required. As soon as a major change occurs (such as a new view model), a new BindingContext will be created and the old one will be cleaned up. The views in Catel will automatically take care of the BindingContext initialization and lifetime management.

Each Binding is a mapping from source to target. It also allows the specification of a converter like available in the XAML platforms. Each Binding also contains several BindingParty objects. The default value for BindingMode is BindingMode.TwoWay.

BindingParty is an object that will take care of watching the source or target of the binding and inform the binding when a value has been changed. The binding parties are considered equal and contain the same logic for both the source and target of the binding.

All bindings must be initialized in the AddBindings method that is available on all views provided by Catel. 


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