XAML-Map-Control/SampleApps/WpfApplication/LocationToVisibilityConverter.cs

using System;
using System.Globalization;
using System.Windows;
using System.Windows.Data;
using MapControl;

namespace WpfApplication
{
    public class LocationToVisibilityConverter : IMultiValueConverter
    {
        public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
        {
            var visibility = Visibility.Hidden;

            if (values.Length == 2 && values[0] is MapBase && values[1] is Point?)
            {
                var parentMap = (MapBase)values[0];
                var position = (Point?)values[1];

                if (position.HasValue &&
                    position.Value.X >= 0d && position.Value.X <= parentMap.ActualWidth &&
                    position.Value.Y >= 0d && position.Value.Y <= parentMap.ActualHeight)
                {
                    visibility = Visibility.Visible;
                }
            }

            return visibility;
        }

        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
        {
            throw new NotSupportedException();
        }
    }
}