How do I tell if an action is a lambda expression?

Question

I am using the EventAgregator pattern to subscribe and publish events. If a user subscribes to the event using a lambda expression, they must use a strong reference, not a weak reference, otherwise the expression can be garbage collected before the publish will execute.

I wanted to add a simple check in the DelegateReference so that if a programmer passes in a lambda expression and is using a weak reference, that I throw an argument exception. This is to help "police" the code.

Example:

eventAggregator.GetEvent<RuleScheduler.JobExecutedEvent>().Subscribe
        (
            e => resetEvent.Set(),
            ThreadOption.PublisherThread,
            false,
            // filter event, only interested in the job that this object started
            e => e.Value1.JobDetail.Name == jobName
        );


public DelegateReference(Delegate @delegate, bool keepReferenceAlive)
    {
        if (@delegate == null)
            throw new ArgumentNullException("delegate");

        if (keepReferenceAlive)
        {
            this._delegate = @delegate;
        }
        else
        {
            //TODO: throw exception if target is a lambda expression
            _weakReference = new WeakReference(@delegate.Target);
            _method = @delegate.Method;
            _delegateType = @delegate.GetType();
        }
    }

any ideas? I thought I could check for @delegate.Method.IsStatic but I don't believe that works... (is every lambda expression a static?)

Answer 1

No, not every lambda-generated delegate is a static method. If there are captured variables it can be an instance. But ultimately there is very little difference between a lambda- based delegate, an anonymous-method- based delegate, and an explicit delegate. I wouldn't do any additional logic - just treat it as a delegate (I would remove the WeakReference code completely).