Allow accessing BindingExpressions to make proper use of `UpdateSourceTrigger=Explicit`

[timschneeb]

Is your feature request related to a problem? Please describe.

I'm trying to use the new UpdateSourceTrigger=Explicit parameter for some bindings.

At the moment, I can't seem to find a way to access BindingExpressions for existing bindings defined in XAML, but I need that to call BindingExpressionBase.UpdateSource.

Describe the solution you'd like

WPF has a public API to retrieve binding expressions:

control.GetBindingExpression(Control.TargetProperty)

Maybe something similar could be implemented.

Describe alternatives you've considered

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Additional context

#13734 also requested this functionality, and although it was closed, there doesn't seem to be any public API for that particular use case yet.

[timunie]

@ThePBone which version did you test? 11.1 beta may have that API now

[timschneeb]

I tested 11.1 beta-1.
UpdateSourceTrigger.Explicit and BindingExpressionBase.UpdateSource are available as mentioned in PR #13970.
However, I don't think there is currently a way to obtain a reference to a BindingExpressionBase for an existing binding using the public API, so the UpdateSource method can't actually be accessed, as far as I can see.

[timunie]

@ThePBone I think you are right. Most likely an oversight

/cc @grokys

[geferon]

Any idea when this will be added? I find myself in need of being able to access the binding(s) of a control