'宣言
Public Class PositionItemInfo
(Of TKey As Class,
TSortKey)
Inherits System.Collections.Generic.Dictionary(Of TKey,PositionItemInfo(Of TKey,TSortKey))
public class PositionItemInfo<TKey,TSortKey> : System.Collections.Generic.Dictionary<TKey,PositionItemInfo<TKey,TSortKey>> where TKey: class