C# extern aliases
January 21st, 2007Few days ago I had a chance to know what "namespace conflict" feel like. This should never happen because good programmer doesn't code anything this way but if it does, there is a solution. For example, we have one class in the first assembly:
{
public class Bar
{
public void Something()
{
// do something here
}
}
}
and a class in the second assembly:
{
public class Bar
{
public void Something()
{
// do something else here
}
}
}
When you try to compile code that use Foo.Bar.Something () you will get an error about ambiguity. Fortunately, with the release of C# 2.0 comes the facility to handle multiple namespace hierarchies, implemented through the extern keyword and compile time configuration.
To use this interesting feature you must follow two steps:
Declare the hierarchies in your code using the extern alias keyword. For example:
extern alias OhMyGod;
// and usual stuff
using System;
using System.IO;
// ...
Remember that extern alias declarations must not be preceded by anything else.
Final step is to pass special option to the compiler:
csc /r:BlahBlah=assembly1.dll /r:OhMyGod=assembly2.dll someother.cs
Now we have two hierarchies that can be accessed uniquely
It works nice but there is one bad thing about it. You cannot use it with ASP.NET compiler because it simply doesn't support a construction like this. That's a pity 
