AssemblyResolve not fired

Question

I am trying to use AssemblyResolve to resolve dependencies for AnyCPU platform.

I have 3 classes:

class Resolver {
    public static void Startup() { }
    static Resolver()
    {
          AppDomain.CurrentDomain.AssemblyResolve += CurrentDomain_AssemblyResolve;
    }

    private static Assembly CurrentDomain_AssemblyResolve(object sender, ResolveEventArgs 
        ...
    }
}

class Foo {
    private ClassFromAssembly _foo;

    public Foo() {
        _foo = new ClassFromAssembly();
    } 
}

class Bar {
    static Bar() {
        Resolver.Setup();
    }

    public voidFoo() {
        var foo = new Foo();
        //...
    } 
}

I am trying to load the ClassFromAssembly class with the AssemblyResolve event. But it seems that AssemblyResolve never fired.

I have two DLLs that contains the ClassFromAssembly one is for x86 and one for x64. I want to dynamically load them when I am on AnyCPU platform, but AssemblyResolve never fired.

Why AssemblyResolve dose not fire?

Answer 1

The behavior you see is caused by method inlining that might be performed by .NET runtime.

To make your scenario work, please ensure that affected method is not inlined. Like so:

class Bar {
    static Bar() {
        Resolver.Setup();
    }

    public voidFoo() {
        _DoTheJob();
    }

    [MethodImpl(MethodImplOptions.NoInlining)]
    void _DoTheJob() {
        var foo = new Foo();
        //...
    }
}

Once method is not inlined, it is guaranteed that your resolver will be installed first, and the assembly containing ClassFromAssembly will be loaded after the resolver is installed.

P.S. Also ensure that assembly of interest is not loaded before you install the assembly resolver. Otherwise, the missed assembly references won't be resolved and those failures will be cached in current AppDomain forever, e.g. you will never get AssemblyResolve event for them again.