How to define the default implementation of an interface in c#?

by

Here comes the black magic:

class Program
{
    static void Main()
    {
        IFoo foo = new IFoo("black magic");
        foo.Bar();
    }
}

[ComImport]
[Guid("C8AEBD72-8CAF-43B0-8507-FAB55C937E8A")]
[CoClass(typeof(FooImpl))]
public interface IFoo
{
    void Bar();
}

public class FooImpl : IFoo
{
    private readonly string _text;
    public FooImpl(string text)
    {
        _text = text;
    }

    public void Bar()
    {
        Console.WriteLine(_text);
    }
}

Notice that not only you can instantiate an interface but also pass arguments to its constructor 🙂

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