This looks brilliant! Thanks a lot!! Stefan

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private: template<class Pwd, class ExpectedPwd> void set_impl( Type const& value , typename boost::enable_if<boost::is_same<Pwd, ExpectedPwd> >::type* enable =0 ) { value_ = value; }

Actually ExpectedPwd is not required as template parameter, but it helps to understand the flow. It is possible to rewrite the Property as:

template<class Type, class PasswordT=void> class Property {

public: Type const& get()const { return value_; }

template<class PwdT> void set( Type const& value) { set_impl<PwdT>(value); }

void set(Type const& value) { set_impl<void>(value); }

private: template<class Pwd> void set_impl( Type const& value , typename boost::enable_if<boost::is_same<Pwd, PasswordT>

...

...

::type* enable =0 ) { value_ = value; }

private: Type value_; };