从参数推断通用类型

Question

Is there any way to infere the type parameter dynamically so that the type of an object is used as another objects type?

I have a generic type called ObjectPrinter that takes a list of the same type it is of in the constructor. It would be neat to not have to declare the type but just have it infered from the argument.

        // This is how i do it. But since myFruits is a list of fruits could not the type Fruit be infered automatically?
        List<Fruits> myFruits = GetFruits();
        var fruitPrinter = new ObjectPrinter<Fruit>(myFruits);

        // Id like to to this   
        List<Fruits> myFruits = GetFruits();
        var fruitPrinter = new ObjectPrinter(myFruits); // and get a ObjectPRinter of type Fruit

Answer 1

Constructors in C# are explicitly not generics - you can't do what you want to do directly. Only member functions can have generic parameters.

However, that tells you what you can do: use a factory function instead of a constructor. Something like this:

public class PrinterFactory {

    public static ObjectPrinter CreatePrinter<T>(List<T> things) {
        return new ObjectPrinter<T>(things);
    }
}

Then you can change your calling code to:

List<Fruit> myFruits = GetFruits();
var fruitPrinter = PrinterFactory.CreatePrinter(myFruits);

And everything should just work.

You can of course put the factory function on whatever class you want.