False CA1812 warning : "internal class that is apparently never instantiated..."

Question

I am getting a code analysis warning that seems to be a false-positive.

CA1812 : Microsoft.Performance : 'MyClass.MyPrivateClass' is an internal class that is apparently never instantiated. If so, remove the code from the assembly. If this class is intended to contain only static methods, consider adding a private constructor to prevent the compiler from generating a default constructor.

How do I get rid of this warning? I prefer to not suppress warnings unless I am sure I couldn't avoid it otherwise.

The classes look like this:

namespace Some.Namespace
{
    public class MyClass
    {
        private class MyPrivateClass
        {
            public int Id { get; set; }
            public ModelObject { get; set; }
        }
    }
}

I use it like this:

private IQueryable<MyPrivateClass> GetMyPrivateClasses()
{
    return this.Repository().All()
        .Select(m => new MyPrivateClass { Id = m.Id, ModelObject = m };
}

Does this usage not count as instantiation?

Answer 1

I guess it is examining the IL; and genuinely - that IL does not ever contain a new MyPrivateClass instruction - because that statement is presumably running against IQueryable<T>, hence that lambda is an expression tree. It will contain some Expression.New, and some typeof(MyPrivateClass) - but no new MyPrivateClass.

In this case, the error is misleading. Simply suppress it.

Answer 2

Change your class to internal or public, that solves the problem. Anyway, you can extract your inner class from the outer class...