Force my code to use my extension method

Question

I'm using BitFactory logging, which exposes a bunch of methods like this:

public void LogWarning(object aCategory, object anObject)

I've got an extension method that makes this a bit nicer for our logging needs:

public static void LogWarning(this CompositeLogger logger, 
      string message = "", params object[] parameters)

Which just wraps up some common logging operations, and means I can log like:

Logging.LogWarning("Something bad happened to the {0}. Id was {1}",foo,bar);

But when I only have one string in my params object[], then my extension method won't be called, instead the original method will be chosen.

Apart from naming my method something else, is there a way I can stop this from happening?

Answer 1

The rules about how overloaded methods are resolved to one (or an error) are complex (the C# specification is included with Visual Studio for all the gory details).

But there is one simple rule: extension methods are only considered if there is no possible member that can be called.

Because the signature of two objects will accept any two parameters, any call with two parameters will match that member. Thus no extension methods will considered as possibilities.

You could pass a third parameter (eg. String.Empty) and not use it in the format.

Or, and I suspect this is better, to avoid possible interactions with additions to the library (variable length argument list methods are prone to this) rename to LogWarningFormat (akin to the naming of StringBuffer.AppendFormat).

PS. there is no point having a default for the message parameter: it will never used unless you pass no arguments: but that would log nothing.