Extending the CultureAndRegionInfoBuilder Class

In the "Extending the CultureInfo Class" section of Chapter 6, I showed a CultureInfoEx class that extends the .NET Framework's CultureInfo class. This CultureInfoEx can be used to hold additional information about a culture; the example given added postal code format information that can be used as a mask for data entry. If you like the idea of custom cultures and you also like the idea of extending the CultureInfo class, then the natural extension is to put both together and have extended custom cultures. Unfortunately, the custom culture architecture is a closed architecture, and this scenario is not supported. A number of barriers prevent the custom culture architecture from being extended:

• CultureAndRegionInfoBuilder is sealed and, therefore, cannot be inherited from.

• The CultureXmlReader and CultureXmlWriter classes that read and write LDML files are both internal and sealed; therefore, they cannot be inherited from and cannot even be accessed.

• The NLP file format is binary and proprietary.

To work around these limitations, you must implement a layer on top of the custom culture architecture. The essential idea is to create a CultureAndRegionInfoBuilderEx class that encapsulates the CultureAndRegionInfoBuilder class. The new class would be a duplicate of the CultureAndRegionInfoBuilder class and would redirect all properties and methods from the "fake" CultureAndRegionInfoBuilderEx class to the CultureAndRegionInfoBuilder class. The Register method would save the additional CultureInfoEx information to a private area in an LDML file (e.g., "bn-BD.ldml"), and this file would be installed in the Windows Globalization folder. The Unregister method would delete/rename the additional file. The Save method would write the additional information to the LDML file, and the CreateFromLdml method would load the additional information from the LDML file. Finally, the CultureInfoEx constructor would check to see if the culture is a custom culture and, if so, would load the additional information from the associated additional information file.