Bug 55373 - [Feature Request] Add at BindingContextChanged event oldValue and newValue
Summary: [Feature Request] Add at BindingContextChanged event oldValue and newValue
Status: RESOLVED ANSWERED
Alias: None
Product: Forms
Classification: Xamarin
Component: Forms ()
Version: unspecified
Hardware: All All
: --- enhancement
Target Milestone: ---
Assignee: Bugzilla
URL:
Depends on:
Blocks:
 
Reported: 2017-04-19 14:05 UTC by workgroupengineering
Modified: 2017-04-19 15:23 UTC (History)
2 users (show)

Tags:
Is this bug a regression?: ---
Last known good build:

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RESOLVED ANSWERED

Description workgroupengineering 2017-04-19 14:05:31 UTC
Hi,
in a library I'm building, i have necessity to get oldValue and newValue in BindingContextChanged event, because i need to subscribe event on new contexet and unsubscribe on old context when the BindingContext is changed.
Comment 1 workgroupengineering 2017-04-19 14:22:55 UTC
I would working a PR, but i have a doubt.

It 'better to change the definition of BindindingContexChanged

so:

public class BindablePropertyChangedEventArgs
{
    public object NewValue {get; Internal sets; }
    public object OldValue {get; Internal sets; }
    public BindableProperty Property {get; Internal sets; }
}

public event EventHandler <BindablePropertyChangedEventArgs> BindingContextChanged;

or so:

public event BindingPropertyChangedDelegate BindingContextChanged
Comment 2 Jimmy [MSFT] 2017-04-19 15:23:40 UTC
Thank you for your feedback! As this would change the existing API, it would be best to create a proposal in our Evolution forum[1] for this so there can be a discussion with the Forms team and community. When submitting a proposal on the Evolution forum, be sure to first read and follow the contribution guidelines[2] so your proposal can be considered. 

[1] https://forums.xamarin.com/categories/xamarin-forms-evolution
[2] https://forums.xamarin.com/discussion/84503/please-read-first