Assembly: System.Xaml (in System.Xaml.dll)
If you do not use the default internal CLR reflection technique for a XamlType, calls to this property can invoke LookupBaseType overrides on XamlType derived classes. For more information about return values and other behavior, see the documentation for LookupBaseType on this type. By default, returns an internal constant that represents an Object if UnderlyingType is null.
LookupBaseType is virtual, and therefore, can be overridden. The override has the potential (whether for malicious purposes or otherwise) to change the reported type information about a XAML type so that it no longer aligns in an expected way with the type system information of its underlying CLR type. For any security-critical checks of assignment operations and access, use the underlying CLR type instead.