Fix binding to interface-inherited properties like IReadOnlyList<T>.Count #32912
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…ount Fixes #13872 The runtime binding expression was not resolving properties inherited from parent interfaces. For example, IReadOnlyList<T>.Count would return null because Count is defined on IReadOnlyCollection<T>, not directly on IReadOnlyList<T>. Added GetProperty() method that searches both base classes and implemented interfaces recursively, similar to how GetIndexer() already handles this case.
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Pull request overview
This PR fixes a bug where runtime bindings failed to resolve properties inherited from parent interfaces. For example, IReadOnlyList<T>.Count would return null because the Count property is defined on IReadOnlyCollection<T>, not directly on IReadOnlyList<T>.
Key changes:
- Added recursive interface search capability to property resolution in runtime bindings
- Refactored property lookup logic into a dedicated
GetProperty()method that mirrors the existingGetIndexer()pattern - Added comprehensive test coverage for the fix across all XAML inflators
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| src/Controls/src/Core/BindingExpression.cs | Adds GetProperty() method with recursive interface search and refactors SetupPart() to use it instead of inline property lookup |
| src/Controls/tests/Xaml.UnitTests/Issues/Maui13872.xaml | XAML test file demonstrating both compiled and uncompiled bindings to IReadOnlyList<T>.Count |
| src/Controls/tests/Xaml.UnitTests/Issues/Maui13872.xaml.cs | Test code-behind with view model and test assertions validating the fix works with all inflators |
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Description
Fixes #13872
Runtime bindings were not resolving properties inherited from parent interfaces. For example,
IReadOnlyList<T>.Countwould returnnullbecauseCountis defined onIReadOnlyCollection<T>, not directly onIReadOnlyList<T>.Changes
GetProperty()method inBindingExpression.csthat searches both base classes and implemented interfaces recursively (similar to howGetIndexer()already handles this case)SetupPart()to use the newGetProperty()methodMaui13872that verifies bindings toIReadOnlyList<T>.Countwork correctly with all XAML inflators (Runtime, XamlC, SourceGen)Test Results
All 1790 XAML unit tests pass: