c# - Why am I getting error CS0246: The type or namespace name could . . . C:\Users\Noob\csharp>csc test cs You haven't added a reference to the DLL You need something like: C:\Users\Noob\csharp>csc test cs r:SnarlNetwork dll (or whatever the assembly is called) Alternatively, if you haven't got it as a separate library, just compile both files: C:\Users\Noob\csharp>csc test cs SnarlNetwork cs