You can produce and consume signed libraries in .NET very easily. In practice it's becoming less common as .NET becomes more open. As an aside, OP says he work

You can produce and consume signed libraries in .NET very easily. In practice it's becoming less common as .NET becomes more open. As an aside, OP says he works with Bart De Smet and they're messing with expression trees. I bet that this is work related to Cortana and the expression trees are used for compiling standing Rx (Reactive Extensions) queries which Cortana uses extensively on the phone and in the cloud.