PostSharp

PostSharp is a development tool for the .NET platform that implements aspect-oriented programming (AOP). It enables cross-cutting concerns to be modularized as reusable aspects and inserted into existing code without invasive edits. Unlike runtime proxies, PostSharp uses compile-time or build-time weaving to inject aspect logic directly into the IL of assemblies.

Aspects are implemented as classes derived from base aspect types such as OnMethodBoundaryAspect, MethodInterceptionAspect, and LocationInterceptionAspect. Developers declare aspects with attributes and apply them to methods, properties, fields, or classes. PostSharp also supports multicast attributes to apply an aspect to many targets with a single declaration.

Weaving is performed by a PostSharp weaver during the build process, typically integrated via MSBuild or NuGet. The result is a modified assembly that contains the injected code, with no requirement for source changes or runtime proxies. This can improve performance and maintainability by keeping cross-cutting behavior in separate, reusable components.

Common use cases include logging, exception handling, input validation, caching, security, and performance instrumentation. Aspects can participate in control flow, handle exceptions, or intercept method calls, including asynchronous ones.

PostSharp is available in a Community Edition (free for open-source and personal use) and several commercial editions that add features such as advanced aspect types, enhanced multicast, centralized configuration, and professional support.