通过反射调用动态加载的DLL方法，但目标引用了一个DLL

Question

I need to dynamically call a method in a bunch of DLLs that are also mine. There is an unknown amount of DLLs to call and they might be in different versions. I dynamically load each DLL and invoke a static method within them using reflection. Basically my code looks like this

foreach (var myThing in instances)
{
    try {
        Assembly a = Assembly.LoadFile(myThing.DllPath);
        Type t = a.GetType("MyNamespace.Services");
        MethodInfo m = t.GetMethod("Backup");
        bool b = (bool)m.Invoke(null, new object[] { "Autobackup"+date+".zip", "Bot" });
    } catch (Exception e){
        LogInternalExceptions(e); // recursively vomit e.InternalException into logs
    }
}

The problem is that the Backup method lives in a static class that references another DLL (log4net).

public static class Services
{
    private static ILog Log = LogManager.GetLogger(typeof(Services));

    public static bool Backup(string filename, string comment)
    {
        // ... snip ...
        Log.Info("Aww right, Princess!");
        return true;
    }
}

So, I get the expected error Could not load file or assembly 'log4net, ...' or one of its dependencies. File not found. Could not load file or assembly 'log4net, ...' or one of its dependencies. File not found. .

I'm sure that this is not my only issue with this method, but it's the first one and I'm stumped. I can edit the caller or the target code, but I don't really know how. The target is an Asp.net MVC3 application, but the class is just a pretty generic general purpose service class.

I would wnat to use something like a preprocessor statement in the target; something like

#if REFLECTION
Log.Info("Aww right, Princess!");
#endif

But I know that makes no sense, because it's not in that stage, how else could I avoid this issue?

Adding log4net reference to the caller project doesn't really solve the big picture. Meaning that if I have some references other than log4net, they would still causes an issue.

Answer 1

Assembly.LoadFile does not resolve dependencies which leads to the exception you describe. Using Load or LoadFrom should resolve your issue.