RegisterGenericDecorator ignores condition

Question

Conditions:

• Autofac: 4.9.1
• .NET Framework: 4.7.2

I have a generic command handler:

public interface ICommand<TResult> : IValidatableObject
{
}

public interface ICommandHandler<TCommand, TResult>
                 where TCommand : ICommand<TResult>, IValidatableObject
{
    TResult Handle(TCommand command);
}

I have a decorator that I want to use for multiple, but not all, implementations of the ICommandHandler (I am going to use a custom attribute to differentiate handlers):

public sealed class LoggingDecorator<TCommand, TResult> : ICommandHandler<TCommand, TResult> 
                              where TCommand : ICommand<TResult>, IValidatableObject
{
    private readonly ICommandHandler<TCommand, TResult> _handler;

    public LoggingDecorator(ICommandHandler<TCommand, TResult> handler)
    {
        _handler = handler;
    }

    public TResult Handle(TCommand command)
    {
        var test = 0;

        return _handler.Handle(command);
    }
}

I am trying to register them with AutoFac as follows:

builder.RegisterAssemblyTypes(ThisAssembly)
               .AsClosedTypesOf(typeof(ICommandHandler<,>))
               .AsImplementedInterfaces();

        builder.RegisterGenericDecorator(
            decoratorType: typeof(LoggingDecorator<,>),
            serviceType: typeof(ICommandHandler<,>),
            condition: _decoratorContext =>
            {
                return false; // true;
            });

Seems like the condition is ignored, the decorator is "assigned" to all handlers always. Have I mis-configured the registration in AutoFac? Or did I miss something else?

How to achieve that the decorator is not registered if the condition returns 'false' in RegisterGenericDecorator method ?

Answer 1

Autofac 4.9.1 is a pretty old version now (3+ yrs). I know that some behaviour around decorator conditions was fixed in v6.0.0; see this issue where upgrading fixed someone's problem that sounds similar to yours.

I'd suggest upgrading to the latest version; if upgrading doesn't fix it, put together a minimal repro and raise an issue on our github repo.