• Now, HxInputBase.FocusAsync focuses InputElement when it is set or throws exception if it is not set.
• InputElement is set only in the descenants (in BuildRenderTree by AddElementReferenceCapture).
• InputElement has no other reason.
• InputElement is a protected property.

Issues:

• The descendants do not know they should (must?) set value to the protected InputElement property.
• The exception message is partialy wrong (they notice only part "focusing too early", not noticing "or InputElement is not set")

Suggestion:

• Remove FocusAsync and InputElement property from HxInputBase and move FocusAsync method only to the components implementing it.
• Or force implementations (HxInputBase descendant) to set InputElement.

FYI, @Arnnes