S3459 — Unassigned members should be removed

Why is this an issue?

Fields and auto-properties that are never assigned to hold the default values for their types. They are either pointless code or, more likely, mistakes.

Noncompliant code example

class MyClass
{
  private int field; // Noncompliant, shouldn't it be initialized? This way the value is always default(int), 0.
  private int Property { get; set; }  // Noncompliant
  public void Print()
  {
    Console.WriteLine(field); //Will always print 0
    Console.WriteLine(Property); //Will always print 0
  }
}

Compliant solution

class MyClass
{
  private int field = 1;
  private int Property { get; set; } = 42;
  public void Print()
  {
    field++;
    Console.WriteLine(field);
    Console.WriteLine(Property);
  }
}

Exceptions

• Fields on types decorated with System.SerializableAttribute attribute.
• Non-static auto-properties with a public set or init accessor, declared inside a private nested type. Since no code outside the enclosing type can reach such a type, a public accessor signals that the property is meant to be populated by reflection-based code. Fields, static properties, get-only properties, and properties with a non-public setter are still reported.

  
  public class ConfigurationLoader
  {
    public string LoadName(string json) =>
      JsonSerializer.Deserialize<Settings>(json).Name;
  
    private class Settings
    {
      public string Name { get; set; } // Compliant: a serializer or model binder can set this property
      public string DisplayName => Name;
    }
  }