//TODO: optim: dont recreate the source binding on each datacontext change, as SourcePropertyPath does not change.
//TODO: optim: don't subscribe to the Changed event if the binding mode does not need it.
protected override void OnDataContextChanged()
{
ClearPathSourceBinding();
_sourceBinding = SourceBindingFactory.CreateBinding(DataContext, Description.SourcePropertyPath);
if (_sourceBinding != null)
{
_sourceBinding.Changed += SourceBindingOnChanged;
}
base.OnDataContextChanged();
}
private void CreateSourceBinding(object source)
{
_dataContext = source;
_sourceBinding = SourceBindingFactory.CreateBinding(source, _bindingDescription.SourcePropertyPath);
if (NeedToObserveSourceChanges)
{
_sourceBinding.Changed += (sender, args) => UpdateTargetFromSource(args.IsAvailable, args.Value);
}
if (NeedToUpdateTargetOnBind)
{
// note that we expect Bind to be called on the UI thread - so no need to use RunOnUIThread here
object currentValue;
bool currentIsAvailable = _sourceBinding.TryGetValue(out currentValue);
UpdateTargetFromSource(currentIsAvailable, currentValue);
}
}
private void UpdateChildBinding()
{
if (_currentChildBinding != null)
{
_currentChildBinding.Changed -= ChildSourceBindingChanged;
_currentChildBinding.Dispose();
_currentChildBinding = null;
}
var currentValue = FieldInfo.GetValue(Source);
if (currentValue == null)
{
// value will be missing... so end consumer will need to use fallback values
return;
}
else
{
_currentChildBinding = SourceBindingFactory.CreateBinding(currentValue, _childTokens);
_currentChildBinding.Changed += ChildSourceBindingChanged;
}
}