If you’re using NInject on a Framework 3.5 project and you start to get fun System.Runtime.CompilerServices.ExtensionAttribute compiler errors, you can do what I did and recompile the NInject source to create happy libraries for 3.5. You may have to alter the nant build script for NInject to not treat warnings as errors to get a successful build but that should do the trick. More info here on this bug in the released NInject libraries.