using System;

using Microsoft.EntityFrameworkCore;

using System.Linq;

using System.Collections.Generic;

​

public class Seller

{

    public int Id { get; set; }

    public string Name { get; set; }    

    public string DocumentNumber { get; set; }  

}

​

public class Product 

{

    public int Id { get; set; }

    public string Name { get; set; }

    public decimal Price { get; set; }

    public int SellerId { get; set; }

}

​

public class MyDbContext : DbContext

{

    public DbSet<Seller> Sellers { get; set; }  

    public DbSet<Product> Products { get; set; }    

}

public class Program

{

    public static void Main()

    {

        var context = new MyDbContext();

        var products = context.Products.ToList();

        var productsOfSeller1 = new List<Product>();

        var productsWithPriceGreaterThenZero = products.Where(i => i.Price > 0M);

        foreach(var product in productsWithPriceGreaterThenZero)

        {

            var seller = context.Sellers.FirstOrDefault(i => i.Id == product.SellerId);

            if(product.SellerId == 1)

            {

                productsOfSeller1.Add(product);

            }

​

            Console.WriteLine($"Product: {product.Name} - Seller: {seller.Name} - Price: {product.Price:C2}");

        }

        var productMostExpensiveSeller1 = productsOfSeller1

            .OrderByDescending(i => i.Price)

            .First();

        Console.WriteLine($"Product of Seller 1 most expensive: {productMostExpensiveSeller1.Name} - Price: {productMostExpensiveSeller1.Price:C2}");

    }

}