Windows.Forms.Timer真实精度究竟是多少？并非文档所述55毫秒

问题背景 #

我需要定期更新UI，System.Windows.Forms.Timer运行在UI线程，看起来是理想选择，但MSDN文档指出：

Windows Forms Timer组件是单线程的，**精度限制为55毫秒。**如果需要更高精度的多线程定时器，请使用System.Timers命名空间下的Timer类。

这让我以为它的间隔值只能是55的倍数，但实际测试结果并非如此：

测试代码 #

private Stopwatch _systemTimersTimerStopwatch = Stopwatch.StartNew();
private Stopwatch _windowsFormsTimerStopwatch = Stopwatch.StartNew();
private long _systemTimersTimerLastElapsed;
private long _windowsFormsTimerLastElapsed;

private void SystemTimersTimer_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
{
    //if (InvokeRequired) {
        BeginInvoke(new MethodInvoker(delegate {
            long elapsed = _systemTimersTimerStopwatch.ElapsedMilliseconds;
            if (_systemTimersTimerLastElapsed != 0) {
                Console.WriteLine($"+ System.Timers.Timer: {elapsed - _systemTimersTimerLastElapsed,2} ms");
            }
            _systemTimersTimerLastElapsed = _systemTimersTimerStopwatch.ElapsedMilliseconds;
        }));
    //}
}

private void WindowsFormsTimer_Tick(object sender, EventArgs e)
{
    long elapsed = _windowsFormsTimerStopwatch.ElapsedMilliseconds;
    if (_windowsFormsTimerLastElapsed != 0) {
        Console.WriteLine($"- Windows.Forms.Timer: {elapsed - _windowsFormsTimerLastElapsed,2} ms");
    }
    _windowsFormsTimerLastElapsed = _windowsFormsTimerStopwatch.ElapsedMilliseconds;
}

测试结果 #

将两个定时器的Interval属性均设为1，输出如下：

+ System.Timers.Timer: 15 ms
- Windows.Forms.Timer: 15 ms
+ System.Timers.Timer: 16 ms
- Windows.Forms.Timer: 20 ms
+ System.Timers.Timer: 15 ms
- Windows.Forms.Timer: 10 ms
+ System.Timers.Timer: 16 ms
- Windows.Forms.Timer: 18 ms
+ System.Timers.Timer: 16 ms
- Windows.Forms.Timer: 14 ms

疑问点 #

• 显然System.Windows.Forms.Timer的精度高于文档所述的55毫秒，这个55毫秒数值的来源是什么？另一篇MSDN文档《Limitations of the Windows Forms Timer Component's Interval Property》并未提及该55毫秒限制。
• 在我的UI更新场景下，使用System.Timers.Timer相比System.Windows.Forms.Timer是否有优势？我认为没有，因为仍需调用BeginInvoke。

内容的提问来源于stack exchange，提问作者RadarNyan