C# 如何在屏幕上显示数据并刷新此数据？

我使用Xamarin.Forms.Maps并显示我的位置和范围内的汽车位置。我每5秒向数据库发送一次获取坐标信息的请求。如何在地图上显示管脚，并在5秒钟后用地图中的新坐标刷新管脚？ 我的代码在这里，但不起作用

  using System;
    using System.Collections.Generic;
    using System.Globalization;
    using System.Threading;
    using System.Threading.Tasks;
    using Xamarin.Forms;
    using Xamarin.Forms.Maps;
    
    namespace CustomRenderer
    {

    public partial class MapPage : ContentPage
    {

   private System.Timers.Timer aTimer;
    public MapPage()
    {
    InitializeComponent();
    SetTimer();
   
    
        }
    
        public void RotateCars()
        {
            customMap.CustomPins = new List<CustomPin>();
    
            double latitudeDoublecar15;
            double longitudeDoublecar15;
    
            var message = new Database();
             CustomPin pin;
            int timestamp = 0;//this timestamo is for cars moving simulation.
            int tmpID15 = 10;//this is temp ID of the car
    
           message.GetCarsApplyPeriodically(Convert.ToString(latitudeDoublecar15), Convert.ToString(longitudeDoublecar15), tmpID15, timestamp);
    
                foreach (var b in Database.car)
                {
                    pin = new CustomPin
                    {
                        Label = b.model,
                        Position = new Position(Convert.ToDouble(b.Latitude, CultureInfo.InvariantCulture), Convert.ToDouble(b.Longitude, CultureInfo.InvariantCulture)),
                        Type = PinType.Place
                    };
                    customMap.Pins.Add(pin);
                    customMap.CustomPins.Add(pin);
                }
    
    
                if (timestamp < 11)
                {
                    timestamp++;
                }
                else
                {
                    timestamp = 0;
                }
    
    
        CustomPin myPin = new CustomPin
                {
                    Type = PinType.Place,
                    Label = DataManager.carsInRange.Count.ToString(),
    
                    Position = new Position(latitudeDoublecar15, longitudeDoublecar15),
                    Address = "my"
    
                };
                customMap.Pins.Add(myPin);
                customMap.CustomPins.Add(myPin);
                customMap.MoveToRegion(MapSpan.FromCenterAndRadius(new Position(latitudeDoublecar15, longitudeDoublecar15), Distance.FromKilometers(0.9)));
    
    Content = customMap;
                Task.Delay(5000);
                customMap.Pins.Clear();
                customMap.CustomPins.Clear();
    
    
            RotateCars();
        }
    }

    
    
   
    private void SetTimer()
    {
    // Create a timer with a five second interval.
    aTimer = new System.Timers.Timer(5000);
    // Hook up the Elapsed event for the timer.
    aTimer.Elapsed += OnTimedEvent;
    aTimer.AutoReset = true;
    aTimer.Enabled = true;
    }
    
    private void OnTimedEvent(Object source, ElapsedEventArgs e)
    {
    RotateCars();
    }

---

在Xamarin中，最好使用Device.StartTimer

Device.StartTimer(TimeSpan.FromSeconds(5),()=> {

     RotateCars();

     return true;
});

---

customMap.CustomPins是实现IPropertyChanged的属性？并尝试使用可观察集合而不是列表。这没有帮助

Device.StartTimer(TimeSpan.FromSeconds(5),()=> {

     RotateCars();

     return true;
});