Compiler Error CS0430
The extern alias 'alias' was not specified in a /reference option
This error occurs when extern Alias is encountered but Alias was not specified as a reference on the command line. To resolve CS0430, compile with /reference.
Example
// CS0430_a.cs
// compile with: /target:library
public class MyClass {}
Compiling with /reference:MyType=cs0430_a.dll to refer to the DLL created in the previous sample resolves this error. The following sample generates CS0430.
// CS0430_b.cs
extern alias MyType; // CS0430
public class Test
{
public static void Main() {}
}