More on full qualification, this time in C#

We were speaking earlier about how to resolve ambiguous enumerated type names in VBScript. Here’s a related C# question I got recently:

namespace Alpha.Bravo.Charlie {
public class Romeo {}
}
namespace Zulu.Alpha.Bravo {
public class Tango {}
}
namespace Zulu.Alpha.Bravo.Charlie {
public class Sierra {
Alpha.Bravo.Charlie.Romeo xray;
// Above line fails, even though it is fully qualified.
Alpha.Bravo.Tango yankee;
// Above line works even though Alpha.Bravo has no such type.
}
}

What the heck is up with that? VBScript was designed to get this right when fully qualified, so why doesn’t C# get it right?

The reason is because the namespace statement doesn’t do what you think it does. The above program is syntactic sugar for this program:

namespace Alpha {
namespace Bravo {
namespace Charlie {
public class Romeo {}
}
}
}
namespace Zulu {
namespace Alpha {
namespace Bravo {
public class Tango {}
namespace Charlie {
public class Sierra {
Alpha.Bravo.Charlie.Romeo xray;
Alpha.Bravo.Tango yankee;
}
}
}
}
}

And now it is clear why the first fails and the second succeeds. C# binds Alpha by searching up the scope chain until it finds a match, and it finds one before it gets to the global Alpha.

This is a rather unfortunate situation. To guarantee that you reallio trulio fully qualify a type in this situation, you can do this in C# v2.0:

global::Alpha.Bravo.Charlie.Romeo xray;

Comments

• Anonymous
  July 15, 2005
  Dude, I think you just BLEW MY MIND! Awesome!
• Anonymous
  July 17, 2005
  Is this a new feature? My C# language spec. says of its Hello World program, "the '::' is not an operator at all".
  
  And it doesn't seem to work in VS2003.
• Anonymous
  July 17, 2005
  Sorry, I should have clarified that this is a new feature.