c# - 检查父属性是否已更改

Question

我创建了一个继承自 System.Windows.Forms.Timer 的新类。在此类中，我创建了另一个计时器作为属性，该属性由父类的计时器启用。子定时器定时器然后报告时间直到下一个父时钟。

我想避免必须使用另一种方法来启动两个计时器。

我能以某种方式检查父 timer.enabled 是否已更改吗？这里的问题是，如果我启动父计时器，我必须等待 timer.Interval 直到它第一次计时。但我希望子计时器从父计时器开始报告第一个滴答的时间。

这是我到目前为止所得到的。

public class LoopTimer : Timer {

    public DateTime? NextTickSchedule { get; set; }

    public LoopTimer() : base() {
        CountdownTimer.Interval = 1000;
        CountdownTimer.Tick += CountdownTimer_Tick;
        this.Tick += LoopTimer_Tick;
    }

    public LoopTimer(IContainer container) : base(container) {
        CountdownTimer.Interval = 1000;
    }

    private void LoopTimer_Tick(object sender, EventArgs e) {
        OnTick();
    }

    private void OnTick() {
        NextTickSchedule = DateTime.Now.AddMilliseconds(this.Interval);
        MinutesUntilNextTick = TimeUntilNextTick.ToString("mm\\:ss");
    }

    public void StartTimer() {
        this.Enabled = CountdownTimer.Enabled = true;
        OnTick();
    }

    public void StopTimer() {
        this.Enabled = CountdownTimer.Enabled = false;
        NextTickSchedule = null;
        MinutesUntilNextTick = "";
        TimeUntilNextTick = new TimeSpan();
    }

    #region Countdown Timer

    public Timer CountdownTimer { get; set; } = new Timer();
    public TimeSpan TimeUntilNextTick { get; set; } = new TimeSpan();
    public string MinutesUntilNextTick { get; set; } = "";

    private void CountdownTimer_Tick(object sender, EventArgs e) {
        if (NextTickSchedule.HasValue) {
            TimeUntilNextTick = NextTickSchedule.Value - DateTime.Now;
            MinutesUntilNextTick = TimeUntilNextTick.ToString("mm\\:ss");
        }
    }

    #endregion
}

Answer 1

您可以覆盖 Enabled 属性并在启用更改时引发事件。然后在子/其他控件中，订阅该事件:

public class MyTimer : Timer
{
    public event EventHandler EnabledChanged;
    public override bool Enabled
    {
        get { return base.Enabled; }
        set
        {
            base.Enabled = value;
            EnabledChanged?.Invoke(this, EventArgs.Empty);
        }
    }
}