Is it the messenger of CommunityToolkit singleton?

Question

I would like to use the messenger of the CommunityToolkit to communicate some view models bewteen them.

If I try to define the dependency injection in this way, I get an exception:

services.AddTransient<IMessenger>();

Because there is no an implementation of the interface.

However, I can register receivers in the constructor of a view model in this way:

WeakReferenceMessenger.Default.Register<MyMessage>(this);

So it seems it is that is a global resource.

So I guess that when a view model send a message, all the receivers get the message, but what happen if only one receiver has to receive the message? I have to check first if the sender is the expected sender.

For example, I have two isolated modules:

public class MainViewModel1

{ ViewModelA _viewModelA; ViewModelB _viewModelB;

public MainViewModel1(ViewModelA paramViewModelA, ViewmodelB paramViewModelB)
{
    _viewModelA = paramViewModelA;
    _viewModelB = paramViewModelB;

    WeakReferenceMessenger.Default.Register<MyMessage>(this);
}

}

public class MainViewModel2 { ViewModelA _viewModelA; ViewModelB _viewModelC;

public MainViewModel2(ViewModelA paramViewModelA, ViewmodelC paramViewModelC)
{
    _viewModelA = paramViewModelA;
    _viewModelC = paramViewModelC;

    WeakReferenceMessenger.Default.Register<MyMessage>(this);
}

}

When the ViewModelA from MainViewModel1 send a message, I only want that is recevied but MainViewModel1, not by MainViewModel2. And When ViewModelA from MainViewModel2 send a message, I only want that mainViewModel2 receives the message.

If I have a general messenger for the whole application, how could handle this case?

Thanks.