An externally visible type extends certain base types. Currently, this rule reports types that derive from the following types:

• System..::.ApplicationException

• System.Xml..::.XmlDocument

• System.Collections..::.CollectionBase

• System.Collections..::.DictionaryBase

• System.Collections..::.Queue

• System.Collections..::.ReadOnlyCollectionBase

• System.Collections..::.SortedList

• System.Collections..::.Stack

For .NET Framework version 1, it was recommended to derive new exceptions from ApplicationException. The recommendation has changed and new exceptions should derive from System..::.Exception or one of its subclasses in the System namespace.

Do not create a subclass of XmlDocument if you want to create an XML view of an underlying object model or data source.

Non-generic Collections

public class MyCollection : CollectionBase
{
}
 
public class MyReadOnlyCollection : ReadOnlyCollectionBase
{
}

public class MyCollection : Collection<T>
{
}
 
public class MyReadOnlyCollection : ReadOnlyCollection<T>
{
}

To fix a violation of this rule, derive the type from a different base type or a generic collection.

Do not suppress a warning from this rule for violations about ApplicationException. It is safe to suppress a warning from this rule for violations about XmlDocument. It is safe to suppress a warning about a non-generic collection if the code was released previously.