[System.ComponentModel.DataObject]
public class PartsBLL
{
    static IEnumerable<Parts> lista = new[] {
            new Parts(){PartID=1,CategoryID=1}, 
            new Parts(){PartID=2,CategoryID=1},
            new Parts(){PartID=3,CategoryID=2},
            new Parts(){PartID=4,CategoryID=2},
            new Parts(){PartID=5,CategoryID=3}
        };
    public IEnumerable<Parts> GetPartsPaged(string PartID, int maximumRows, int startRowIndex)
    {

        if (!string.IsNullOrEmpty(PartID))
            return lista.Where(p => p.PartID.ToString().Equals(PartID));
        else
            return lista.Skip(startRowIndex).Take(1);
    }
    public void UpdatePart(int CategoryID, int PartID)
    {
        Parts pa = lista.ToList().Find(p => p.PartID.Equals(PartID));
        pa.CategoryID = CategoryID;
    }
    public int SelectCount(string PartID)
    {
        return 5;
    }
}