XAML-Map-Control/MapControl/WPF/MapPolypoint.WPF.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Media;

namespace MapControl;

public partial class MapPolypoint : MapPath
{
    protected void UpdateData(IEnumerable<Location> locations, bool closed)
    {
        using var context = ((StreamGeometry)Data).Open();

        if (ParentMap != null && locations != null)
        {
            var longitudeOffset = GetLongitudeOffset(locations);

            AddPolylinePoints(context, locations, longitudeOffset, closed);
        }
    }

    protected void UpdateData(IEnumerable<IEnumerable<Location>> polygons)
    {
        using var context = ((StreamGeometry)Data).Open();

        if (ParentMap != null && polygons != null)
        {
            var longitudeOffset = GetLongitudeOffset(polygons.FirstOrDefault());

            foreach (var locations in polygons)
            {
                AddPolylinePoints(context, locations, longitudeOffset, true);
            }
        }
    }

    private void AddPolylinePoints(StreamGeometryContext context, IEnumerable<Location> locations, double longitudeOffset, bool closed)
    {
        var points = locations.Select(location => LocationToView(location, longitudeOffset));

        if (points.Any())
        {
            var start = points.First();
            var polyline = points.Skip(1).ToList();
            var minX = start.X;
            var maxX = start.X;
            var minY = start.Y;
            var maxY = start.Y;

            foreach (var point in polyline)
            {
                minX = Math.Min(minX, point.X);
                maxX = Math.Max(maxX, point.X);
                minY = Math.Min(minY, point.Y);
                maxY = Math.Max(maxY, point.Y);
            }

            if (maxX >= 0d && minX <= ParentMap.ActualWidth &&
                maxY >= 0d && minY <= ParentMap.ActualHeight)
            {
                context.BeginFigure(start, true, closed);
                context.PolyLineTo(polyline, true, true);
            }
        }
    }
}