MEF Exception Unwrapper

MEFExtensions.cs

/// <summary>
/// Attempts to retrieve the real cause of a composition failure.
/// </summary>
/// <remarks>
/// Sometimes a MEF composition fails because an exception occurs in the ctor of a type we're trying to
/// create. Unfortunately, the CompositionException doesn't make that easily available, so we don't get
/// that info in haystack. This method tries to find that exception as that's really the only one we care
/// about if it exists. If it can't find it, it returns the original composition exception.
/// </remarks>
/// <param name="exception"></param>
/// <returns></returns>
public static Exception UnwrapCompositionException(this Exception exception)
{
    var compositionException = exception as CompositionException;
    if (compositionException == null)
    {
        return exception;
    }

    var unwrapped = compositionException;
    while (unwrapped != null)
    {
        var firstError = unwrapped.Errors.FirstOrDefault();
        if (firstError == null)
        {
            break;
        }
        var currentException = firstError.Exception;

        if (currentException == null)
        {
            break;
        }

        var composablePartException = currentException as ComposablePartException;

        if (composablePartException != null
            && composablePartException.InnerException != null)
        {
            var innerCompositionException = composablePartException.InnerException as CompositionException;
            if (innerCompositionException == null)
            {
                return currentException.InnerException ?? exception;
            }
            currentException = innerCompositionException;
        }

        unwrapped = currentException as CompositionException;
    }

    return exception; // Fuck it, couldn't find the real deal. Throw the original.
}