using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var account = new Account(){

        Id = 1

        };

        //account.Include();

        account.IncludeX(m => m.Domains);

        //string[] names = { "Jon", "Marc", "Joel", "Thomas", "Copsey", "Konrad", "Andrew", "Brian", "Bill" };

        //var result = names.IncludeX(a => a.Length);

        //Console.WriteLine(result.Count());

    }

}

​

public static class ModelExtensions

{

    public static IEnumerable<L> Include<T, L>(

        this IBase model, Func<T, L> lengthProvider) where T : L, new()

    {

        //return names

            //.OrderBy(a => lengthProvider(a))

            //.ThenBy(a => a);

        T obj = new T();

       //T.Domains 

        Console.WriteLine("Extension method called on BaseClass object");

        return null;

    }

    public static void IncludeX<T, L>(

        this T baseObject, Func<T, L> xx) //where T : L, new()

    {

        var child = xx(m=>m).GetType();

        Console.WriteLine(child.Name);

        Console.WriteLine("Extension method called on BaseClass object");

    }

}

​

public class IBase{}

public class Account : IBase

{

public int Id {get; set;}

public List<Domain> Domains {get; set;}

}

​

public class Domain

{

public int Id {get; set;}

public string? Name {get; set;}

}