Convert rows from a data reader into typed results

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Do you really need a list, or would IEnumerable be good enough?

I know you want it to be generic, but a much more common pattern is to have a static Factory method on the target object type that accepts a datarow (or IDataRecord). That would look something like this:

public class Employee
{
    public int Id { get; set; }
    public string Name { get; set; }

    public static Employee Create(IDataRecord record)
    {
        return new Employee
        {
           Id = record["id"],
           Name = record["name"]
        };
    }
}

.

public IEnumerable<Employee> GetEmployees()
{
    using (var reader = YourLibraryFunction())
    {
       while (reader.Read())
       {
           yield return Employee.Create(reader);
       }
    }
}

Then if you really need a list rather than an IEnumerable you can call .ToList() on the results. I suppose you could also use generics + a delegate to make the code for this pattern more re-usable as well.

Update: I saw this again today and felt like writing the generic code:

public IEnumerable<T> GetData<T>(IDataReader reader, Func<IDataRecord, T> BuildObject)
{
    try
    {
        while (reader.Read())
        {
            yield return BuildObject(reader);
        }
    }
    finally
    {
         reader.Dispose();
    }
}

//call it like this:
var result = GetData(YourLibraryFunction(), Employee.Create);

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