Listing 10-44 extracted from chapter The .NET 2 type system from a C#2 point of view

Listing 10-43<     > Listing 10-45

This listing can be compiled with the command line:
csc.exe /target:exe Example_10_44.cs
Errors: 1 Warnings: 0

class Program {
   static void Main() {
      bool? b = null;
      // Cannot implicitly convert type 'bool?' to bool.
      if ( b ) { /*...*/ } 
   }
}