I would suggest writing an extension method for this:
public static IEnumerable<T> Select<T>(this IDataReader reader,
Func<IDataReader, T> projection)
{
while (reader.Read())
{
yield return projection(reader);
}
}
You can then use LINQ's ToList() method to convert that into a List<T> if you want, like this:
using (IDataReader reader = ...)
{
List<Customer> customers = reader.Select(r => new Customer {
CustomerId = r["id"] is DBNull ? null : r["id"].ToString(),
CustomerName = r["name"] is DBNull ? null : r["name"].ToString()
}).ToList();
}
I would actually suggest putting a FromDataReader method in Customer (or somewhere else):
public static Customer FromDataReader(IDataReader reader) { ... }
That would leave:
using (IDataReader reader = ...)
{
List<Customer> customers = reader.Select<Customer>(Customer.FromDataReader)
.ToList();
}
(I don't think type inference would work in this case, but I could be wrong...)