How to convert sqldatareader to list of dto's?

Question

I just started moving all my ado.net code from the asp.net pages to repo's and created dto's for each table (manually), but now I don't know what is a good efficient way to convert a sqldatareader to a list of my dto objects?

For example sake, my dto is Customer.

I am using webforms and I am NOT using an ORM. I would like to start slow and work my way up there.

Answer 1

Here a short example on how you can retrieve your data using a data reader:

var customers = new List<Customer>();
string sql = "SELECT * FROM customers";
using (var cnn = new SqlConnection("Data Source=Your_Server_Name;Initial Catalog=Your_Database_Name;Integrated Security=SSPI;")) {
    cnn.Open();
    using (var cmd = new SqlCommand(sql, cnn)) {
        using (SqlDataReader reader = cmd.ExecuteReader()) {
            // Get ordinals (column indexes) from the customers table
            int custIdOrdinal = reader.GetOrdinal("CustomerID");
            int nameOrdinal = reader.GetOrdinal("Name");
            int imageOrdinal = reader.GetOrdinal("Image");
            while (reader.Read()) {
                var customer = new Customer();
                customer.CustomerID = reader.GetInt32(custIdOrdinal);
                customer.Name = reader.IsDBNull(nameOrdinal) ? null : reader.GetString(nameOrdinal);
                if (!reader.IsDBNull(imageOrdinal)) {
                    var bytes = reader.GetSqlBytes(imageOrdinal);
                    customer.Image = bytes.Buffer;
                }
                customers.Add(customer);
            }
        }
    }
}

If a table column is nullable then check reader.IsDBNull before retrieving the data.