Question

I have a windows 7 x64 desktop with vs2010 and a virtual box installation of linux with mono and monodevelop. I compile the following program with vs2010 and run it in the linux virtual machine and it fails with a seemingly uncatchable FileNotFoundException. If I compile it in the virtual machine and run it in windows, it works great.

The problem seems to be that an uncatchable exception is tossed by mono before Main() when it is impossible to load a dll. Is there a way to restructure my program or coerce mono such that I can catch this exception?

I am trying to write a single program that has an interface in either WPF or GTK according to what is available at runtime.

using System;  
#if __MonoCS__  
using Gtk;  
#else  
using System.Windows;  
#endif  
using System.IO;  
using System.Runtime.CompilerServices;  
using System.Collections.Generic;  

namespace Test {

 public static class Program {

  [STAThread]
  public static void Main() {
   try {
    Main2();
   } catch (FileNotFoundException e) {
    Console.WriteLine("Caught FileNotFoundException");
    Console.WriteLine("FileName = {0}", e.FileName);
   }
  }

  [MethodImpl(MethodImplOptions.NoInlining)]
  public static void Main2() {
#if __MonoCS__  
   Application.Init();  
#else  
   Window w = new Window();  
#endif  
  }

 }

}

Answer 1

You are exposing yourself to the implementation details of the JIT-compiler. The exact time it will throw the exception for the missing assembly depends on how eagerly it translates the IL into machine code. I know the Microsoft jitter is truly just-in-time, it compiles one method at a time, just before it is about to execute. Although this is affected by whether or not a debugger is attached. You’re dead in the water if Mono, say, compiles the entire class. The jitter will throw before Main() can start.

Maybe it will work better if you put Main2() in another class. The best thing to do is just have an assembly available, a dummy if necessary.