Why FileNotFoundException when I Assembly.Load an

Question

In my Windows Azure role C# code I do the following:

Assembly.Load( "Microsoft.WindowsAzure.ServiceRuntime" );

and FileNotFoundException is thrown. The problem is an assembly with such name is present and has even loaded before the code above is run - I see a corresponding line in the debugger "Output" window and when I do:

AppDomain.CurrentDomain.GetAssemblies().Any(
    assembly => assembly.FullName.StartsWith("Microsoft.WindowsAzure.ServiceRuntime"));

the result is true and if I use Where(), then SingleOrDefault() I get a reference to a corresponding Assembly object.

Why can't I load an assembly with Assembly.Load()?

Answer 1

That Load() call can only succeed if Microsoft.WindowsAzure.ServiceRuntime.dll is stored in your app's probing path. By default the same directory as your EXE. Problem is, it isn't stored there, it is stored in the GAC.

The point of the GAC is to act as a depository of assemblies with the same name but different [AssemblyVersion]s, culture or processor architecture. Which is the problem with your Load(), you don't specify any. There is no reasonable way that fusion can pick an assembly for you, it is apt to give you the wrong one. So it doesn't bother, even if there is only one to pick from.

Specifying the full AsssemblyName.FullName is required. Use Project + Add Reference to avoid.

Answer 2

The documentation for Assembly.Load says that you're meant to supply the full name for the assembly (including e.g. version information).

Using just a plain name for the assembly will fail if the assembly is normally loaded from e.g. the GAC. E.g.:

        try
        {
            Assembly.Load("System");
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.ToString());
        }

        Console.WriteLine(AppDomain.CurrentDomain.GetAssemblies().Any(
        assembly => assembly.FullName.StartsWith("System")));
        Console.ReadLine();

Exhibits similar behaviour.

Answer 3

You should load it with a full assembly qualified name.

Answer 4

From the MSDN documentation:

// You must supply a valid fully qualified assembly name.            
        Assembly SampleAssembly = Assembly.Load
            ("SampleAssembly, Version=1.0.2004.0, Culture=neutral, PublicKeyToken=8744b20f8da049e3");