// @nuget: Microsoft.EntityFrameworkCore.SqlServer

// @nuget: Z.EntityFramework.Extensions.EFCore  

​

using System.Linq;

using Microsoft.EntityFrameworkCore;

using System.Collections.Generic;

using Microsoft.Data.SqlClient; 

​

​

public class Program

{

    public static void Main()

    {

        using (var context = new EntityContext())

        {

            context.Database.EnsureCreated();

        }

        using (var context = new EntityContext())

        {

            context.Customers.Add(new Customer() { Name ="Customer1", Country = "UK" });

            context.Customers.Add(new Customer() { Name ="Customer2", Country = "USA" });

            context.Customers.Add(new Customer() { Name ="Customer3", Country = "USA" });

            context.BulkSaveChanges();  

        }

        using (var context = new EntityContext())

        {

            var query  = context.Customers.GroupBy(a=>a.Name).Select(p=>p.First());

            var list = query.ToList();

            FiddleHelper.WriteTable(list);

            System.Console.WriteLine(list.Count());

            System.Console.WriteLine(query.Count());                 

​

        }

    }

​

    public class EntityContext : DbContext

    {

        public EntityContext() 

        {

        }

​

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)

        {

            optionsBuilder.UseSqlServer(new SqlConnection(FiddleHelper.GetConnectionStringSqlServer()));

​

            base.OnConfiguring(optionsBuilder);

        }

        public DbSet<Customer> Customers { get; set; }

    }

    public class Customer

    {

        public int ID { get; set; }

        public string Name { get; set; }

        public string Country { get; set; }

    }

}