"The initial work was done by Scott Peterson and then I take taken over and continue developing and advancing the feature. The implementation was rather straightforward especially because C# 4.0 only supports covariance and contravariance on delegates and interfaces. The trickiest and most challenging part was to upgrade type inference to deal with variant type arguments and to provide a meaningful error reporting.
"Optional parameters
"Optional parameters as of C# 4.0 are limited to the CLR 2.0 functionality which in plain speak essentially means that only constant expressions are supported. The feature adds what VB supported for quite some time but does not add anything new although the integration with existing features like nullable types has been done."
