Again one of those things which looks so simple, but could drive one mad during debugging.
Much before Optional Parameters came in, C# developers used to depend on Method Overloading for mimicking Optional Parameters. Consider a scenario where both exists, what would be the output ?
The output would be :
The reason behind this is the overload resolution method adopted when we have a overloaded method and a method with optional parameter. Here is what MSDN says.
If two candidates are judged to be equally good, preference goes to a candidate that does not have optional parameters for which arguments were omitted in the call. This is a consequence of a general preference in overload resolution for candidates that have fewer parameters.
ByteLanguage.Net 