``++public static++`` mutable fields of classes which are accessed directly should be protected to the degree possible. This can be done by reducing the accessibility of the field or by changing the return type to an immutable type.
This rule raises issues for ``++public static++`` fields with a type inheriting/implementing ``++System.Array++`` or ``++System.Collections.Generic.ICollection<T>++``.
* If the field is ``++readonly++`` and is initialized inline with an immutable type (i.e. inherits/implements one of the types in the previous list) or null.