Lots of `Avalonia.Markup.UnitTests` were failing intermittently. This is because in release mode, in a method like this:
```
[Fact]
public void SetValue_Should_Return_False_For_Missing_Object()
{
var data = new Class1();
var target = new ExpressionObserver(data, "Next.Bar");
using (target.Subscribe(_ => { }))
{
Assert.False(target.SetValue("baz"));
}
}
```
`data` can get GC'ed at any point after creating target. Added `GC.KeepAlive()` calls to prevent this.
Fixes#1035Fixes#1036Fixes#1037
`ExpressionSubject` wasn't a good name as the important thing it isn't
convert an `ExpressionObserver` into an `ISubject`. The important thing
it does is insert an `IValueConverter` into the pipeline.
This reverts commit 57e646583f.
For TextBox there can be 2 bindings to Text: one which is the binding to the
view model which should have data validation enabled, and another binding to
the TextPresenter in the template which should not have data validation
enabled, or it will override the view model data validation. For this we need
to be able to distinguish between the two and so bindings with data validation
enabled need to always send BindingNotifications.
Conflicts:
src/Avalonia.Base/AvaloniaObject.cs
tests/Avalonia.Markup.Xaml.UnitTests/Data/BindingTests_Validation.cs
Steven Kirk
Wiesław Šoltés
Wiesław Šoltés
Jeremy Koritzinsky
Steven Kirk