Design advice. Using DataTable or List<MyObject> for a generic rule checker

Answer 1

Well, using DataTable does not preclude use of LINQ

table.Rows.Cast<DataRow>() //IEnumerable<DataRow>, linq it to death

This guy makes some arguments about HashTable vs. DataTable and this guy finds Dictionary better than DataTable, but not by much (factors in Dictionary create cost).

Note: if the columns are known beforehand (that is, a user may select some of the columns from a predefined set of columns(name, type)), I would go with strongly typed classes, since data["property"] does not get Intellisense support like data.Property does.