S3453 — Classes should not have only "private" constructors

Why is this an issue?

When a class has only a private constructor, it can’t be instantiated except within the class itself. Such classes can be considered dead code and should be fixed

Exceptions

• Classes that access their private constructors (singletons or smart enums) are ignored.
• Classes containing only static members, nested types, or both are ignored. Classes with only static members are covered by Rule S1118.
• Classes that derive from SafeHandle since they can be instantiate through P/Invoke.

How to fix it

Code examples

Noncompliant code example

public class MyClass // Noncompliant: the class contains only private constructors
{
  private MyClass() { ... }
}

Compliant solution

public class MyClass // Compliant: the class contains at least one non-private constructor
{
  public MyClass() { ... }
}

Resources

Documentation

• S1118 - Utility classes should not have public constructors
• Microsoft Learn - SafeHandle Class
• Microsoft Learn - Platform Invoke (P/Invoke)
• Microsoft Learn - Use enumeration classes instead of enum types
• Wikipedia - Dead code
• Wikipedia - Singleton pattern

Articles & blog posts

• C# in Depth - Implementing the Singleton Pattern in C#
• Medium - Making enums smarter in C#