non CLS-compliant classes in SDK, what that means?
When you browse SharePoint SDK , you come across some classes such as
ContentByQueryWebPart which is marked as non CLS-compliant classes. This class or any derived type may not be interoperable with a wide range of .Net supported programming languages.Something that you really need to consider when using this calss or driving your custom types off of it. Generally, C# complier does not check for CLS compliance of your code and you have to explicitly instruct it to do so.
This class for whatever reason is not decorated to be CLS-compliant and it should be used with extra caution in regards to interoperability.
[CLSCompliant(false)]
public class ContentByQueryWebPart : CmsDataFormWebPart
{
.....
}