In Visual J# .NET 2005, the compiler does automatic CLS Compliance checking. This is especially useful when developers want to write libraries usable from multiple languages.
The CLS rules standardize things such as data types and how objects are exposed and interoperate. For a framework to be usable from multiple languages it is essential that it conforms to these rules. If a component uses only CLS features in the API it exposes to other code (including derived classes), the component is guaranteed to be accessible from any programming language that supports the CLS. Components that adhere to the CLS rules and use only the features included in the CLS are said to be CLS-compliant components. Developers can now choose to have the J# compiler automatically check for such compliance.