Static Class

ID

csharp.static_class

Severity

low

Remediation Complexity

medium

Remediation Risk

low

Remediation Effort

medium

Resource

Code Smell

Language

CSharp

Tags

code-style, design

Description

Reports plain classes whose members are all static and could therefore be declared static class. A private parameter-less constructor (the pre-2.0 idiom for a hidden constructor) is tolerated.

Rationale

A static class documents the design intent — "this type is a namespace for related helpers, it is never instantiated" — and the compiler enforces it. Without the modifier the class can be instantiated, inherited from and extended with instance state by a later edit, and consumers cannot tell at a glance that those operations are unintended. Marking the type static removes the ambiguity and turns accidental misuse into a compile error.

public class MathHelpers                 // FLAW
{
    public static int Add(int a, int b) => a + b;
    public static int Mul(int a, int b) => a * b;
}

public static class StringHelpers        // OK, already static
{
    public static string Trim(string s) => s?.Trim() ?? string.Empty;
}

public class Counter                     // OK, holds instance state
{
    private int _count;
    public void Inc() => _count++;
}

Remediation

Add the static modifier to the class declaration and remove any leftover parameter-less private constructor; the compiler will then forbid future instance members.

References