There are two ways you can develop ASP.NET projects with Visual Studio: ASP.NET Web Applications and ASP.NET Web Sites. The difference between these two variants of ASP.NET projects lays in the way the way the “code behind” is built:

  1. In ASP.NET Web Applications, the code behind is built by Visual Studio using MSBuild.
  2. In ASP.NET Web Sites, the code behind is built by ASP.NET itself, or precompiled by the ASP.NET precompiler aspnet_compiler.exe.

Historically, it has always been possible to use PostSharp with ASP.NET Web Applications since PostSharp naturally integrates with any MSBuild project.

Things have been more complex with ASP.NET Web Sites. I developed an assembly post-processor that hooks into the ASP.NET build process and calls the PostSharp command-line utility just after the C# compiler. It worked – as a hack may work: sometimes, in best cases.

But there are good reasons not to use PostSharp with ASP.NET Web Sites:

  • Performance issues: You probably don't want to load the CPU of your build server by an extra build step. Remember that PostSharp is about 10x slower than the C# compiler itself. If you want your web sites to start in reasonable time on web servers (where CPU is usually scarce), refrain for using PostSharp this way. Workaround: use precompiled web sites.
  • Licensing issues: PostSharp is licensed for uses by developers. PostSharp does not offer a single license for use on web servers. If you're using PostSharp on a web server, you're probably breaking the license agreement. Workaround: use precompiled web sites.
  • Functionality issues: Unlike ASP.NET Web Applications, which are built into a single assembly, the ASP.NET Web Sites build pipeline breaks a single web site into multiple small assemblies. This may break some PostSharp functionalities.

So I had to take a decision with this, here it is:

The use of PostSharp 2.0 with ASP.NET Web Sites is officially unsupported by SharpCrafters. Unofficially, we released the assembly post-processor on CodePlex as PostSharp4AspNet under the permissive Ms-PL license, so you can still use it at your own risks. But you have been warned.

Happy PostSharping!

-gael