In Telerik OpenAccess ORM, you can use LINQ queries to retrieve data from the database as persistent classes. You should use the IObjectScope.Extent<T>() extension method (where T is the persistent class) as the entity from which you're about to retrieve records.

var result = from p in scope.Extent()

             where p.UnitPrice > 4

             select p;

this.radGridView1.DataSource = result.ToList();