CSHARP.CLASS.ACIC : Ambiguous Call from Inner Class (C#)

Summary

A method call from an inner class is ambiguous.

This checker identifies problems related to the definition of inner classes. Namely, inner classes can be defined in C# as static or non-static. The former cannot directly access instance fields of the outer class, while the latter have the ability to refer to the instance of the outer class passed at time of their creation and consequently also to its instance fields. However, this comes at the price of embedding an implicit reference, in each instance of the inner class, to the wrapping instance of the outer class, which makes objects larger and prevents garbage collection of the outer instance. This can result in memory exhaustion. Moreover, non-static inner classes expose the risk of ambiguity for method calls that could refer to both local methods and methods of the outer class.

Properties

WARNING_FILTER += discard class="Ambiguous Call from Inner Class (C#)"

Example

namespace DocumentationExamples
{
    public class InnerClasses
    {
        public static void Main(string[] args)
        { }

        public virtual void Foo() { }
        public class InnerClassesC1
        {
            public void Foo() { }
            public void Test()
            {
                Foo(); // "Ambiguous Call from Inner Class (C#)" warning issued here 
                       // - this ambiguity might be a risk to code correctness. 
            }
        }
    }
}

The programmer should for instance rewrite InnerClassesC1 as follows.

public class InnerClassesC1
{
    public void Moo() { }
    public void Test()
    {
        Moo();
    }
}

Resolution

Check if inner classes can be made static, consequently saving memory and reducing the burden on the garbage collector. Avoid using synonyms for methods in the inner class and in the outer class.

Relevant Configuration File Parameters

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

• REPORT_SIMILAR_WARNINGS
• WARNING_FILTER