CSHARP.CLASS.STATICMOD : Static Field Assigned Non-Static (C#)

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CSHARP.CLASS.STATICMOD : Static Field Assigned Non-Static (C#)

Summary

Static fields can be updated from a static context, but this is a bad programming practice:

In object-oriented code, fields should mostly be instance fields; static fields should be used in rare situations, such as for constants. This checker looks for static fields that are assigned from non-static contexts. It only considers as acceptable assignments that are used for the lazy initialization of static fields, although they might occur in non-static contexts. That is current programming practice.

Properties

Example

using System;
using System.Collections;
using System.Collections.Generic;

namespace DocumentationExamples
{

    public class StaticFieldAccess1
    {
        private static int[] scores = new int[100];
        private static int next;
        public static void Main(string[] args)
        {
            new StaticFieldAccess1();
        }
        public void AddScore(int score)
        {
            if (next < scores.Length)
                scores[next++] = score;                       // Two "Static Field Assigned Non-Static (C#)" warnings issued here:
                                                              // - one for 'next' 
                                                              // - one for 'scores' 
        }
        public float Average()
        {
            float sum = 0.0f;
            for (int pos = 0; pos < next; pos++)
                sum += scores[pos];
            return sum / next;
        }
    }

    public class StaticFieldAccess2
    {
        private static IDictionary session;
        private static IDictionary session2;
        public IDictionary GetSession()
        {
            if (session == null)
            {
                Console.WriteLine("Initializing session");
                session = new Dictionary<string, string> ();                             // ok: correct lazy initialization idiom
            }
            return session;
        }
        public IDictionary GetSession2()
        {
            if (session == null)                                                               // The programmer probably intended to check session2 here
            {
                Console.WriteLine("Initializing session2");
                session2 = new Dictionary<string, string> (); // "Static Field Assigned Non-Static (C#)" warning issued here
            }
            return session2;
        }
    }
}

In this example, the programmer should replace the static fields with instance fields:

  private int[] scores = new int[100];
  private int next;

Resolution

Check if static fields can be replaced by instance fields or if methods can be made static.

Relevant Configuration File Parameters

The following configuration file parameters affect checks for this warning class.