Listing 9-11 extracted from chapter Fundamental concepts of the language

Listing 9-10<     > Listing 9-12

This listing can be compiled with the command line:
csc.exe /out:Program.exe /target:exe Example_9_11_to_rename_Program.cs /r:Asm1.dll /r:Asm2.dll
Errors: 0 Warnings: 0

using FooIO = Foo.IO;
using CusIO = Custom.IO;
class Program{
   static void Main(){
      FooIO.Stream stream1 = new FooIO.Stream();
      CusIO.Stream stream2 = new CusIO.Stream();   
   }
}