How do I add a .Net assembly reference in Unity?

Unity Engine
1

I want to synchronize different Unity editor with System.Messaging.

I just put the System.Messaging.dll from

in my project folder. Every thing compiles but if I try to run the following line in Unity

if (MessageQueue.Exists("foo"))

I get

Any ideas?

2

Looks like its built for .NET 3.5. Unity’s version of Mono is only compatible with .NET 2.0.

Or something like those numbers.