C# conditional attribute on interface member

Question

I'm trying to get rid of the "#if TRACE" directives in my code, by using the Conditional attribute instead, but can't apply this approach easily to interfaces. I have a way round this but it's pretty ugly, and I'm looking for a better solution.

E.g. I have an interface with a conditionally compiled method.

interface IFoo
{
#if TRACE
    void DoIt();
#endif
}

I can't use the conditional attribute in an interface:

// Won't compile.
interface IFoo
{
    [Conditional("TRACE")]
    void DoIt();
}

I could have the interface method just call a conditional private method in the concrete class:

interface IFoo
{
    void TraceOnlyDoIt();
}

class Foo : IFoo
{
    public void TraceOnlyDoIt()
    {
        DoIt();
    }

    [Conditional("TRACE")]
    void DoIt()
    {
        Console.WriteLine("Did it.");
    }
}

This would leave my client code with redundant calls to the 'nop' TraceOnlyDoIt() method in a non-TRACE build. I can get round that with a conditional extension method on the interface, but it's getting a bit ugly.

interface IFoo
{
    void TraceOnlyDoIt();
}

class Foo : IFoo
{
    public void TraceOnlyDoIt()
    {
        Console.WriteLine("Did it.");
    }
}

static class FooExtensions
{
    [Conditional("TRACE")]
    public static void DoIt(this IFoo foo)
    {
        foo.TraceOnlyDoIt();
    }
}

Is there a better way to do this?

Answer 1

A trace method shouldn't be appearing on an interface as it's an implementation detail.

But if you're stuck with the interface, and can't change it, then I'd use the #if ... #endif approach that you started with.

It is a rather savage syntax though, so I sympathise with why you might want to avoid it...