Description of Change

Allow binding to Native (non-BP) Views.

Each platform now expose SetBinding(string propertyName, BindingBase binding) as an extension method on the respective native views (UIView, Android.View, FrameworkElement).

To get 2-Way Bindings to work, SetBinding can take an additional updateSourceEventName argument. On iOS, if the Property of the UIView is Observable, the updateSourceEventName is not mandatory. On [U]WP, something similar is done in order to try to get 2-Way bindings to behave even without the updateSourceEventName.

In addition to this, the platforms also expose SetValue(BindableProperty property, ...) and SetBinding(BindableProperty property, ...). Those will have no effect unless the view happen to be directly wrapped in a Xamarin.Forms Layout. In that case, those (attached) BindableProperties will be transferred to the wrapper, allowing this kind of code to be valid.

var btn = new UIKit.Button();
btn.SetValue(Grid.RowProperty, 2); 

var grid = new Xamarin.Forms.Grid ();
grid.Children.Add(btn.ToView());

The SetBindingContext is not meant to be invoked directly, but it's used by the platform.

The value of this will make more sense when the Xaml support is added.

Bugs Fixed

None

API Changes

Added:
iOS:

• public static void SetBinding(this UIView view, string propertyName, BindingBase binding, string updateSourceEventName = null);
• public static void SetBinding(this UIView self, BindableProperty targetProperty, BindingBase binding);
• public static void SetValue(this UIView target, BindableProperty targetProperty, object value);
• public static void SetBindingContext(this UIView target, object bindingContext, Func<UIView, IEnumerable<UIView>> getChildren = null);

Android

• public static void SetBinding(this global::Android.Views.View view, string propertyName, BindingBase binding, string updateSourceEventName = null);
• public static void SetBinding(this global::Android.Views.View view, BindableProperty targetProperty, BindingBase binding);
• public static void SetValue(this global::Android.Views.View target, BindableProperty targetProperty, object value);
• public static void SetBindingContext(this global::Android.Views.View target, object bindingContext, Func<global::Android.Views.View, IEnumerable<global::Android.Views.View>> getChildren = null);

[U]WP

• public static void SetBinding(this FrameworkElement view, string propertyName, BindingBase binding, string updateSourceEventName = null);
• public static void SetBinding(this FrameworkElement view, BindableProperty targetProperty, BindingBase binding);
• public static void SetValue(this FrameworkElement target, BindableProperty targetProperty, object value);
• public static void SetBindingContext(this FrameworkElement target, object bindingContext, Func<FrameworkElement, IEnumerable<FrameworkElement>> getChildren = null);

PR Checklist

• Has tests (if omitted, state reason in description)
• Rebased on top of master at time of PR
• Changes adhere to coding standard
• Consolidate commits as makes sense