Strange behavior with actions, local variables and garbage collection in MVVM light Messenger

Question

I am having a really strange problem with the Messenger system in MVVM Light. It\'s hard to explain, so here is small program that demonstrates the issue:

Answer 1

I agree, the behavior of this program is really strange.

I tried it myself and as you already figured out the problem is somehow related to this line:

var x = target;

I have no idea why this line causes any trouble but you might consider this workaround:

class Program
    {
        static void Main(string[] args)
        {
            var prog = new Program();
            var recipient = new object();

            prog.RegisterMessageA(recipient);
            prog.RegisterMessageB(recipient);

            prog.SendMessage("First Message");
            GC.Collect();
            prog.SendMessage("Second Message");
        }

        public void RegisterMessageA(object target)
        {
            Messenger.Default.Register(target, (Message msg) =>
            {
                Console.WriteLine(msg.Name + " received by A");
                var x = msg.Target;
            });
        }

        public void RegisterMessageB(object target)
        {
            Messenger.Default.Register(target, (Message msg) =>
            {
                Console.WriteLine(msg.Name + " received by B");
            });
        }

        public void SendMessage(string name)
        {
            Messenger.Default.Send(new Message { Name = name });
        }

        class Message : MessageBase //part of the MVVM Light framework
        {
            public string Name { get; set; }
        }
    }

MessageBase is a class from the MVVM Light Framework which offers the possibility to retrieve the target from the message itself.

But I'm not sure if this is what you're trying to achieve...