Method Could Be Static

ID

csharp.method_could_be_static

Severity

info

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Efficiency

Language

CSharp

Tags

best-practice, efficiency

Description

Reports a private instance method that never touches instance state — no this, no base, and no unqualified reference to an instance field, property or method of the enclosing class. Such a method does not need an instance and can be declared static.

Rationale

A method that ignores instance state is conceptually a free function. Marking it static documents that it has no per-instance dependency, lets the compiler and JIT skip the implicit this argument, and makes the method callable and testable without constructing the type. The rule is deliberately limited to private methods so that making it static never changes a type’s public contract, an override, or an interface implementation.

public class Calculator
{
    private int factor = 2;

    // FLAW — uses only its parameters, no instance state
    private int Add(int a, int b) => a + b;
    private int Square(int x) => x * x;          // FLAW — could be static

    // OK — reads the instance field 'factor'
    private int Scale(int x) => x * factor;

    // OK — already static
    private static int Triple(int x) => x * 3;
}

Remediation

Add the static modifier to the method. If the method later needs instance state, the modifier can simply be removed again.

References