List of objects plus a tag

Question

I want to store a list of objects, lets say of type Car, but with an additional 'tag' property eg a boolean True/False which does not belong on the Car class. What is the best way to accomplish this? I need to pass the result between methods.

Answer 1

You could use a tuple of some sort, like Pair<T,U>.

Heres an exemple:

namespace TestProject.Utils
{
    public class Pair<T, U>
    {    
        public Pair(T first, U second)
        {
            this.First = first;
            this.Second = second;
        }

        public T First { get; set; }
        public U Second { get; set; }
    }
}

For C#4, here's a good read about tuple : CLR Inside Out - Building Tuple

EDIT : Usage

Car mustang;
List<Pair<Car, bool>> list = new List<Pair<Car, bool>>(); // <Car, isAwesome> pairs..
list.Add(new Pair(mustang, true));

Answer 2

Dictionary<Car, bool> carFlags = new Dictionary<Car, bool>();

You can pass the car into the dictionary and get back the bool flag.

Answer 3

Using inheritance, you can create a CarWithTag class that extends the Car class without polluting the Car class with unneeded properties:

public class Car
{
    public string CarInfoEtcetera { get; set; }
}

public class CarWithTag : Car
{
    public string Tag { get; set; }
}

Then you can create a method that accepts a CarWithTag object when you need to pass tag info as well.

    private string GetCarTagInfo(CarWithTag car)
    {
        return car.Tag;
    }

Now you can new up a CarWithTag object and pass it into the method, along with any Car info.

        CarWithTag carWithTag = new CarWithTag()
                                    {
                                        Tag = "123abc", 
                                        CarInfoEtcetera = "etc"
                                    };

        string tag = GetCarTagInfo(carWithTag);