CODEWITHSUNDEEP
c#.net
Joseph Willcoxson
Joseph Willcoxson

Reputation: 6040

Assembly.Load and its weirdness... "Could not find file or assembly" error

Our localization team was trying to use LocBaml (.NET Framework version, 4.6.1) to localize some resources. They kept on getting errors saying "Could not find file or assembly..." So, I looked into it, saw the note that the x.resources.dll file had to be in same directory as x.dll. ("x" just means some name). Tried that, still go the same error. I then built a debug version and also downloaded the .NET source code. Turns out some exception was occuring in the guts of .NET. If I could summarize, it was failing when trying to do Assembly.Load("x"). So I wrote a program trying to duplicate the situation...

using System;
using System.Reflection;
using System.Linq;

namespace Nothing
{
   class Loader
   {
      public static void Main(string[] args)
      {
         try
         {
            if (args.Count() == 1)
            {
               Assembly asm = Assembly.Load(args[0]);

               Console.WriteLine($"Name of asembly: {asm.FullName}");
            }
            else
            {
               Console.WriteLine("Need to specify filename");
            }
         }
         catch (Exception x)
         {
            Console.WriteLine("Exception: {0}", x);
         }
      }
   }
}

The file was named AsmLoader.cs and compiled to AsmLoader.exe.

Well from the directory x.dll was in, I typed in \path\to\AsmLoader.exe x.dll and \path\to\AsmLoader.exe x. Same error, "Could not find file or assembly..."

Looked at the stack trace for the exception and saw that "codebase" was an argument for some function on the stack. Gave it a thought, and copied AsmLoader.exe to the same directory as x.dll.

Gave .\AsmLoader.exe x.dll a try..still same error. Remembered that the argument to the exception was just "x". Tried .\AsmLoader.exe x .... bingo... worked. For grins, copied LocBaml.exe and it's .config file to the same directory, and tried .\LocBaml x.resources.dll ... ding, ding, ding... success. Finally.

So, for now, I'll just tell the localiztion team to copy LocBaml to the same directory as the files and all should be good.

However, I can't help but feel this could somehow be solved with code. How can I make changes to the code in the example so that AsmLoader.exe doesn't have to be in the same directory as the DLL I want to load? I had even changed my path environment variable to ensure AsmLoader.exe and both x.dll directories were in the path. That didn't work...

So what do I need to change for it to work in my base program...and then maybe I can do the same for LocBaml...???

Upvotes: 0

Views: 1225

Answers (1)

Joseph Willcoxson
Joseph Willcoxson

Reputation: 6040

Well, I came up with a solution to add an AssemblyResolve event handler to the current app domain. Solved it for this simple example and my rebuilt LocBaml...

In main, add:

AppDomain.CurrentDomain.AssemblyResolve += LoadFromCurrentDirectory;

Implement LoadFromCurrentDirectly like:

static Assembly LoadFromCurrentDirectory(object sender, ResolveEventArgs args)
{
   string name = args.Name;

   bool bCheckVersion = false;
   int idx = name.IndexOf(',');
   if (idx != -1)
   {
      name = name.Substring(0, idx);
      bCheckVersion = true;
   }

   string sCurrentDir = Directory.GetCurrentDirectory();

   if (!name.EndsWith(".dll", StringComparison.OrdinalIgnoreCase) && !name.EndsWith(".exe"))
   {
      string[] exts = { ".dll", ".exe" };
      foreach( string ext in exts)
      {
         string tryPath = Path.Combine(sCurrentDir, name + ext);
         if (File.Exists(tryPath))
         {
            name = name += ext;
            break;
         }
      }
   }

   string path = Path.Combine(sCurrentDir, name);
   if (!string.IsNullOrEmpty(path) && File.Exists(path))
   {
      Assembly assembly = Assembly.LoadFrom(path);
      if (assembly != null & bCheckVersion)
      {
         if (assembly.FullName != args.Name)
            return null;
      }
      return assembly;
   }
   else
   {
      var reqAsm = args.RequestingAssembly;

      if (reqAsm != null)
      {
         string requestingName = reqAsm.GetName().FullName;
         Console.WriteLine($"Could not resolve {name}, {path}, requested by {requestingName}");
      }
      else
      {
         Console.WriteLine($"Could not resolve {args.Name}, {path}");
      }
   }
   return null;
}

I'm sure it could be optimized to add a global list of directories, or to use the path when searching for files to load. However, for our use case, works just fine. When I added it to our LocBaml code, it solved the loading problem for us...also got rid of necessity of copying the en\x.resources.dll files to our output directory. As long as we run the program from the output directory, LocBaml finishes parsing.

Upvotes: 2

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