using System;
using Insight.Database;
using Npgsql;

namespace Insight
{
    public interface IRepository
    {
        [Sql("SELECT a + b FROM (SELECT :a AS a, :b AS b) AS t")]
        int Sum(IBar bar);
    }

    public interface IFoo
    {
        int A { get; set; }
    }

    public interface IBar : IFoo
    {
        int B { get; set; }
    }

    public class Bar : IBar
    {
        public int A { get; set; }
        public int B { get; set; }
    }

    class Program
    {
        static void Main()
        {
            const string connectionString = "MY_CONNECTION_STRING";
            var connection = new NpgsqlConnection(connectionString).As<IRepository>();
            Console.WriteLine(connection.Sum(new Bar { A = 42, B = 13 }));
        }
    }
}