Unused Private Field

ID

csharp.unused_private_field

Severity

low

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Code Smell

Language

CSharp

Tags

CWE:563, code-style, unused-code

Description

Reports private fields that are never referenced anywhere in their declaring type. Because a private field is only reachable from within its own type, a field with no references is dead code.

Rationale

An unreferenced private field wastes memory, lengthens the type, and invites confusion about whether it carries state that matters. Fields decorated with an attribute are excluded: a serializer, DI container, or engine ({@code [JsonProperty]}, {@code [DataMember]}, {@code [SerializeField]}) may read or write them by reflection, so "no source reference" does not mean unused. Compile-time const declarations are a separate construct and are not reported.

public class Cache
{
    private int hits;                   // OK — used in Record
    private int misses;                 // FLAW — never referenced
    private readonly string name;       // FLAW — never referenced

    [System.Text.Json.Serialization.JsonInclude]
    private int total;                  // OK — touched by serialization

    public void Record()
    {
        hits++;
    }
}

Remediation

Delete the unused field. If it was meant to hold state, add the code that reads it; if it is populated only by a framework, confirm the attribute that makes that explicit is present.

References