// sync
Product produto = null;
using (var cn = new SqlConnection(configuration.GetConnectionString("DefaultConnection")))
{
    var query = @"
                    SELECT * FROM Products WHERE ProductID = @Id
                    SELECT * FROM  [Order Details] WHERE ProductID = @Id
                    ";
    using (var result = cn.QueryMultiple(query, new { id }))
    {
        produto = result.Read<Product>().Single();
        produto.OrderDetails = result.Read<OrderDetail>().ToList();
    }
}
// async
Product produto = null;
using (var cn = new SqlConnection(configuration.GetConnectionString("DefaultConnection")))
{
    var query = @"
                    SELECT * FROM Products WHERE ProductID = @Id
                    SELECT * FROM  [Order Details] WHERE ProductID = @Id
                    ";
    using (var result = await cn.QueryMultipleAsync(query, new { id }))
    {
        produto = await result.ReadFirstAsync<Product>();
        produto.OrderDetails = (await result.ReadAsync<OrderDetail>()).ToList();
    }
}