Why is DataTable faster than DataReader

Question

So we have had a heated debate at work as to which DataAccess route to take: DataTable or DataReader.

DISCLAIMER I am on the DataReader side and the

Answer 1

SqlDataAdapter.Fill calls SqlCommand.ExecuteReader with CommandBehavior.SequentialAccess set. Maybe that's enough to make the difference.

As an aside, I see your IDbReader implementation caches the ordinals of each field for performance reasons. An alternative to this approach is to use the DbEnumerator class.

DbEnumerator caches a field name -> ordinal dictionary internally, so gives you much of the performance benefit of using ordinals with the simplicity of using field names:

foreach(IDataRecord record in new DbEnumerator(reader))
{
    artifactList.Add(new ArtifactString() {
        FormNumber = (int) record["FormNumber"],
        FormOwner = (int) record["FormOwner"],
        ...
    });
}

or even:

return new DbEnumerator(reader)
    .Select(record => new ArtifactString() {
        FormNumber = (int) record["FormNumber"],
        FormOwner = (int) record["FormOwner"],
        ...
      })
    .ToList();