using System;

using System.Data.SqlClient;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    private static HashSet<SqlConnection> instances = new HashSet<SqlConnection>();

    public static void Main()

    {

        IEnumerable<object> results = Results();

        Console.WriteLine("executing any()");

        if(results.Any())

        {

            // noop

        }

        foreach(object result in results)

        {

            Console.WriteLine(result);

        }

        Console.WriteLine("Connection instances created: " + instances.Count());

        foreach(SqlConnection sql in instances)

        {

            // finally clause on using closes

            Console.WriteLine(sql.State);   

        }

    }

    private static IEnumerable<object> Results()

    {

        string sql = "SELECT * FROM OrderDetails where OrderDetailID = 1";

        using (SqlConnection connection = new SqlConnection(FiddleHelper.GetConnectionStringSqlServerW3Schools()))

        {       

            instances.Add(connection);  

            Console.WriteLine("query running...");

            SqlCommand command = new SqlCommand(sql, connection);

            connection.Open();

            using (SqlDataReader reader = command.ExecuteReader())

            {

                Console.WriteLine(reader.GetHashCode());

                while (reader.Read())

                {

                    yield return reader[0];

                }

            }

        }

        Console.WriteLine("query finish...");

    }

}