Duplicate names in a XAML namescope are not permitted.
Notes to Implementers
Do not permit duplicate names to be registered. If the input name is already assigned to an existing element in the internal collection representation of the XAML namescope (even if it is the same as scopedElement), throw an exception.
Also consider throwing an exception if the provided name does not conform to XamlName Grammar.
Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)