Static Class Design
Note
This content is reprinted by permission of Pearson Education, Inc. from Framework Design Guidelines: Conventions, Idioms, and Patterns for Reusable .NET Libraries, 2nd Edition. That edition was published in 2008, and the book has since been fully revised in the third edition. Some of the information on this page may be out-of-date.
A static class is defined as a class that contains only static members (of course besides the instance members inherited from System.Object and possibly a private constructor). Some languages provide built-in support for static classes. In C# 2.0 and later, when a class is declared to be static, it is sealed, abstract, and no instance members can be overridden or declared.
Static classes are a compromise between pure object-oriented design and simplicity. They are commonly used to provide shortcuts to other operations (such as System.IO.File), holders of extension methods, or functionality for which a full object-oriented wrapper is unwarranted (such as System.Environment).
✔️ DO use static classes sparingly.
Static classes should be used only as supporting classes for the object-oriented core of the framework.
❌ DO NOT treat static classes as a miscellaneous bucket.
❌ DO NOT declare or override instance members in static classes.
✔️ DO declare static classes as sealed, abstract, and add a private instance constructor if your programming language does not have built-in support for static classes.
Portions © 2005, 2009 Microsoft Corporation. All rights reserved.
Reprinted by permission of Pearson Education, Inc. from Framework Design Guidelines: Conventions, Idioms, and Patterns for Reusable .NET Libraries, 2nd Edition by Krzysztof Cwalina and Brad Abrams, published Oct 22, 2008 by Addison-Wesley Professional as part of the Microsoft Windows Development Series.