Handle ReflectionTypeLoadException during MEF composition

Question

I am using a DirectoryCatalog in MEF to satisfy imports in my application. However, there are sometimes obfuscated assemblies in the directory that cause a

Answer 1

I was doing this from an API I was writing and the SafeDirectoryCatalog would not log multiple exports matching a single import from different assemblies. MEF debugging is typically done via debugger and TraceListener. I already used Log4Net and I didn't want someone to need to add another entry to the config file just to support logging. http://blogs.msdn.com/b/dsplaisted/archive/2010/07/13/how-to-debug-and-diagnose-mef-failures.aspx I came up with:

    // I don't want people to have to add configuration information to get this logging. 
    // I know this brittle, but don't judge... please. It makes consuing the api so much
    // easier.
    private static void EnsureLog4NetListener()
    {
        try
        {
            Assembly compositionAssembly = Assembly.GetAssembly(typeof (CompositionContainer));
            Type compSource = compositionAssembly.GetType("System.ComponentModel.Composition.Diagnostics.CompositionTraceSource");

            PropertyInfo canWriteErrorProp = compSource.GetProperty("CanWriteError");
            canWriteErrorProp.GetGetMethod().Invoke(null,
                                                    BindingFlags.Public | BindingFlags.NonPublic |
                                                    BindingFlags.Static, null, null,
                                                    null);

            Type traceSourceTraceWriterType =
                compositionAssembly.GetType(
                    "System.ComponentModel.Composition.Diagnostics.TraceSourceTraceWriter");

            TraceSource traceSource = (TraceSource)traceSourceTraceWriterType.GetField("Source",
                                                                          BindingFlags.Public |
                                                                          BindingFlags.NonPublic |
                                                                          BindingFlags.Static).GetValue(null);

            traceSource.Listeners.Add(new Log4NetTraceListener(logger));                
        }
        catch (Exception e)
        {
            logger.Value.Error("Cannot hook MEF compisition listener. Composition errors may be swallowed.", e);
        }
    }