using System;

​

public class Program

{

    public class Product

    {

        public string Field1 { get; set; }

        public int Field2 { get; set; }

    }

​

    public class ProductDto

    {

        public string Field1 { get; set; }

        public int Field2 { get; set; }

    }

​

    public interface IProductFieldBuilder<T>

    {

        T BuildField();

    }

​

    public class ProductFieldBuilder1 : IProductFieldBuilder<string>

    {

        public string BuildField() => "Field1";

    }

​

    public class ProductFieldBuilder2 : IProductFieldBuilder<int>

    {

        public int BuildField() => 1;

    }

​

    public class ProductBuilderBase

    {

        protected event Action<ProductDto, Product> actions;

​

        public Product BuildProduct(ProductDto productDto)

        {

            var product = new Product();

            actions?.Invoke(productDto, product);

            return product;

        }

    }

​

    public class ProductBuilder1 : ProductBuilderBase

    {

        public ProductBuilder1(IProductFieldBuilder<string> b1, IProductFieldBuilder<int> b2)

        {

            actions += (x, y) => y.Field1 = b1.BuildField();

            actions += (x, y) => y.Field2 = b2.BuildField();

        }

    }

​

    public class ProductBuilder2 : ProductBuilderBase

    {

        public ProductBuilder2(IProductFieldBuilder<string> b1)

        {

            actions += (x, y) => y.Field1 = b1.BuildField();

        }

    }

​

    public static void Main()

    {

        var dto = new ProductDto();

        var pb1 = new ProductBuilder1(new ProductFieldBuilder1(), new ProductFieldBuilder2());

        var r1 = pb1.BuildProduct(dto);

        var pb2 = new ProductBuilder2(new ProductFieldBuilder1());

        var r2 = pb2.BuildProduct(dto);

​

        Console.ReadKey();

    }

}