private static void ReadOrderData(string connectionString)
{
    string queryString = "SELECT OrderID, CustomerID FROM dbo.Orders;";
    using (SqlConnection connection = new SqlConnection(connectionString))
    {
        SqlCommand command = new SqlCommand(queryString, connection);
        connection.Open();
        SqlDataReader reader = command.ExecuteReader();
        try
        {
            while (reader.Read())
            {
                Console.WriteLine(String.Format("{0}, {1}",     reader[0], reader[1]));
            }
        }
        finally
        {
            reader.Close();
        }
    }
}

private SQLConnection CreateConnection()
{
    var connection = new SqlConnection(_connectionString);
    connection.Open();
    return connection;
}

private List<int> ReadOrderData()
{
    using(var connection = CreateConnection())
    using(var command = connection.CreateCommand())
    {
        command.CommandText = "SELECT OrderID FROM dbo.Orders;";

        using(var reader = command.ExecuteReader())
        {
            var results = new List<int>();
            while(reader.Read()) results.Add(reader.GetInt32(0));
            return results;
        }
    }
}

using (var conn = new SqlConnection(cs))
{
    var dogs = connection.Query("select name, age from dogs");

    foreach (dynamic dog in dogs)
    {
        Console.WriteLine("{0} age {1}", dog.name, dog.age);
    }
}

using (var conn = new SqlConnection(cs))
{
    var dogs = connection.Query<Dog>("select Name, Age from dogs");

    foreach (Dog dog in dogs)
    {
        Console.WriteLine("{0} age {1}", dog.Name, dog.Age);
    }
}

class Dog
{
    public string Name { get; set; }
    public int Age { get; set; }
}

public void ExecuteWithDataReader(string sql, Action<DataReader> stuffToDo) {
    using (SqlConnection connection = new SqlConnection(connectionString)) {
        using (SqlCommand command = new SqlCommand(sql, connection)) {
            connection.Open();

            using (SqlDataReader reader = command.ExecuteReader()) {
                try {
                    while (reader.Read()) {
                        stuffToDo(reader);
                    }
                }
                finally {
                    reader.Close();
                }
            }
        }
    }
}


private static void ReadOrderData(string connectionString) {
    string sql = "SELECT OrderID, CustomerID FROM dbo.Orders;";

    ExecuteWithDataReader(sql, r => Console.WriteLine(String.Format("{0}, {1}", r[0], r[1])));
}

private List<int> ReadOrderData()
{
    return ExecuteList<int>("SELECT OrderID FROM dbo.Orders;",
        x => x.GetInt32("orderId")).ToList();
}

private IEnumerable<T> ExecuteList(string query,
    Func<IDataRecord, T> entityCreator)
{
    using(var connection = CreateConnection())
    using(var command = connection.CreateCommand())
    {
        command.CommandText = query;
        connection.Open();
        using(var reader = command.ExecuteReader())
        {
            while(reader.Read())
               yield return entityCreator(reader);
        }
    }
}

using(var db = new MyDataContext())
{
  var items = db.Orders.Select(item => new { item.OrderID, item.CustomerID })
                       .ToList();
  items.ForEach(item => Console.WriteLine("{0} {1}", item.OrderID, item.CustomerID);
}

using(conn = new sqlconnection)
    using(cmd = new sqlcommand) {
          // blah blah blah
    }

private SQLConnection CreateConnection()
{
    var connection = new SqlConnection(_connectionString);
    connection.Open();
    return connection;
}

public static DataTable StatisticsGet( Guid tenantId ) {
    DataTable result = new DataTable();
    result.Locale = CultureInfo.CurrentCulture;

    Database db = DatabaseFactory.CreateDatabase(DatabaseType.Clients.ToString());

    using (DbCommand dbCommand = db.GetStoredProcCommand("reg.StatsGet")) {
        db.AddInParameter(dbCommand, "TenantId", DbType.Guid, tenantId);

        result.Load(db.ExecuteReader(dbCommand));
    } // using dbCommand

    return result;
} // method::StatisticsGet