如何在Xamarin.Forms.maps.map上显示选择器

<maps:Map x:Name="myMap" />

private async void ShowLocationOnMap(string address)
{
    var geocoder = new Geocoder();
    var locations = await geocoder.GetPositionsForAddressAsync(address);
    if (locations != null && locations.Any())
    {
        var position = locations.First();
        myMap.MoveToRegion(MapSpan.FromCenterAndRadius(position, Distance.FromMiles(1)));
        var pin = new Pin
        {
            Position = position,
            Label = "Selected Location"
        };
        myMap.Pins.Add(pin);
    }
}