Passing parameters/properties with MEF

Question

Consider the following sample:
I have a Car class and an ILogger interface. I'd like the ILogger implementations to log (console, file, db, etc) a list of cars' specs. And of course, I want to use MEF for ILogger. But for logging, my logger class should have access to a car's specification. And I'm not sure what would be the best way to pass objects to my logger classes. To be more clear, here's some code:

class Program
{
    public class Car
    {
        public string Brand { get; set; }
        public string Model { get; set; }
    }

    private CompositionContainer _container;

    [Import(typeof(ILogger))]
    public ILogger logger;

    private Program()
    {
        var catalog = new AggregateCatalog();
        catalog.Catalogs.Add(new AssemblyCatalog(typeof(Program).Assembly));
        this._container = new CompositionContainer(catalog);
        this._container.ComposeParts(this);
    }

The ILogger interface should get a Car object for logging. And I'm not sure whether I should pass it in logger's constructor or as a Property, or just a method parameter.

Using property: If I use a property for passing a car, the ILogger interface looks like this:

public interface ILogger
{
    Car Car { get; set; }
    void Log();
}

And I can iterate through my list items as below:

static void Main(string[] args)
{
    Program p = new Program(); // Composition is performed in the constructor
    var cars = new List()
        {
            new Car() { Brand = "Nissan", Model = "SkyLine" },
            new Car() { Brand = "Porche", Model = "Carrera"},
            new Car() { Brand = "Ferrari", Model = "Enzo"}
        };
    foreach (var car in cars)
    {
        p.logger.Car = car;
        p.logger.Log();
    }
    Console.ReadKey();
}

Using parameter: The interface:

public interface ILogger
{
    void Log(Car car);
}

and the program:

foreach (var car in cars)
{
    p.logger.Log(car);
}

Using constructor: This is where I seem to be lost. I can change the ILogger interface to :

public interface ILogger
{
    Car Car {get; set;}
    void Log();
}

And in the implemented class:

[Export(typeof(ICarLogger))]
public class ConsoleLogger : ICarLogger
{
    public Car Car { get; set; }
    [ImportingConstructor]
    public ConsoleLogger(Car car)
    { 
        this.Car = car;
    }
    public void Log()
    {
        Console.WriteLine("Brand: {0}\tModel: {1}", Car.Brand, Car.Model);
    }
}

But this leads to creating the CompositionContainer everytime I want to pass a new value to the constructor (By using ComposeExportedValue method). Put it simply, How can I pass various variables to the constructor without having to rebuild the whole CompositionContainer again?

So, which of these 3 approaches are better in your opinion. And how can I implement the constructor approach as mentioned? Hope I described my problem clearly.
Thanks and apologies for the lengthy question.
P.S. I'm using the MEF version which comes with .Net 4.

Did you want to instantiate a new ILogger for each car? Or, as @blindmeis suggests, an IEnumerable<Car> within the ILogger? I had a similar issue, see my answer to: stackoverflow.com/q/9626227/210709 — IAbstract

blindmeis blindmeis · Accepted Answer · 2012-03-15T13:17:51

you wrote you wanna log a list of cars, so shouldnt it be:

public interface ILogger
{
   void Log(IEnumerable<Car> cars);
}

Passing parameters/properties with MEF

1 Answers