Aspect-oriented programming (AOP) methodology is evolving from research projects towards commercial applications. Most of the existing ACIP tools suitable for commercial projects are intended for Java platform only which limits their applicability. Known ACIP tools for Microsoft.NET such as Aspect#, Loom.NET, etc. are still at experimental stage. Most of them lack flexibility and comfortable user interface. Aspect.NET, our AOP framework for Microsoft.NET, offers a new approach taking the best of Microsoft.NET specifics. Aspect.NET allows to define aspects using any language implemented for NET that supports the concept of attribute. For aspect specification, we developed very simple and compact language-agnostic AOP meta-language - Aspect.NET.ML. At the source code layer, aspect definition in Aspect.NET looks like the code of a compilation unit annotated by Aspect.NET.ML constructs. The AOP annotations are converted into specific AOP custom attributes used by the Aspect.NET tool. Thus, an aspect assembly ke