Compiler Error CS2034
A /reference option that declares an extern alias can only have one filename. To specify multiple aliases or filenames, use multiple /reference options.
To specify two aliases and/or file names, use two /reference options, like this:
Example
The following code will generate error CS2034.
// CS2034.cs
// compile with: /r:A1=cs2034a1.dll;A2=cs2034a2.dll
// to fix, compile with: /r:A1=cs2034a1.dll /r:A2=cs2034a2.dll
// CS2034
extern alias A1;
extern alias A2;
using System;