設計模式 (C#) 實戰：狀態模式 — 實體類與抽象狀態基類定義 (中)

MessageModel — 實體類別

public class MessageModel
{
    public MessageModel(string msg, DateTime pt)
    {
        _message = msg; _publishTime = pt;
    }
    private string _message;
    public string Message { get => _message; set => _message = value; }
    private DateTime _publishTime;
    public DateTime PublishTime { get => _publishTime; set => _publishTime = value; }
}

AbstractMessageState — 抽象狀態基類

public abstract class AbstractMessageState
{
    protected Message _message;
    public Message Message { get => _message; set => _message = value; }

    public abstract void StateChangeCheck();
    public abstract List Get();
    public abstract bool Insert(MessageModel mm);
}

設計要點

• 抽象類別持有 Message (Context) 參考，具體狀態可存取 Context 狀態決定切換
• 三個抽象方法定義狀態行為合約：StateChangeCheck (切換判斷)、Get、Insert
• Context 與具體狀態雙向關聯：Context 持有抽象狀態，狀態持有 Context — 形成協作閉環