Parsing SPListItem is slower than parsing DataRow

Question

I use a SPQuery to get a list of 100 items. I then loop round the list and get the values of the SPListItem

e.g. string name = mySPListItem["Name"].ToString(); (VERY SLOW)

This runs a lot slower than converting the SPListItemCollection to a datatable (SPListItemCollection.GetDataTable()) and then looping over each datarow.

e.g. string name = myDataRow["Name"].ToString(); (VERY FAST)

Can anyone explain why this is?

More code as requested.

        foreach (System.Data.DataRow dr in nListItemCollection.GetDataTable().Rows)
        {
            returnVar.Add(new myObj(dr)); //Fast
        }

        SPListItemCollection items = mySPList.Items;
        foreach (SPListItem dr in items)
        {
            SPListItem li = dr;
            myObj n = new myObj(li); //Slow
            returnVar.Add(n);
        }

Answer 1

To explain it simply, the SP version needs to do quite a bit more to get a column value than when all columns/rows are retrieved at once and parsed as a native c# DataRow.