XAML-Map-Control/MapControl/Shared/MapProjectionFactory.cs

using System;

namespace MapControl;

public class MapProjectionFactory
{
    public MapProjection GetProjection(string crsId)
    {
        var projection = CreateProjection(crsId);

        if (projection == null &&
            crsId.StartsWith("EPSG:") &&
            int.TryParse(crsId.Substring(5), out int epsgCode))
        {
            projection = CreateProjection(epsgCode);
        }

        return projection ?? throw new NotSupportedException($"MapProjection \"{crsId}\" is not supported.");
    }

    protected virtual MapProjection CreateProjection(string crsId)
    {
        MapProjection projection = crsId switch
        {
            WebMercatorProjection.DefaultCrsId => new WebMercatorProjection(),
            WorldMercatorProjection.DefaultCrsId => new WorldMercatorProjection(),
            Wgs84UpsNorthProjection.DefaultCrsId => new Wgs84UpsNorthProjection(),
            Wgs84UpsSouthProjection.DefaultCrsId => new Wgs84UpsSouthProjection(),
            EquirectangularProjection.DefaultCrsId or "CRS:84" => new EquirectangularProjection(crsId),
            _ => null
        };

        if (projection == null && crsId.StartsWith(StereographicProjection.DefaultCrsId))
        {
            projection = new StereographicProjection(crsId);
        }

        return projection;
    }

    protected virtual MapProjection CreateProjection(int epsgCode)
    {
        return epsgCode switch
        {
            var c when c is >= Etrs89UtmProjection.FirstZoneEpsgCode
                        and <= Etrs89UtmProjection.LastZoneEpsgCode => new Etrs89UtmProjection(c % 100),
            var c when c is >= Nad83UtmProjection.FirstZoneEpsgCode
                        and <= Nad83UtmProjection.LastZoneEpsgCode => new Nad83UtmProjection(c % 100),
            var c when c is >= Wgs84UtmProjection.FirstZoneNorthEpsgCode
                        and <= Wgs84UtmProjection.LastZoneNorthEpsgCode => new Wgs84UtmProjection(c % 100, true),
            var c when c is >= Wgs84UtmProjection.FirstZoneSouthEpsgCode
                        and <= Wgs84UtmProjection.LastZoneSouthEpsgCode => new Wgs84UtmProjection(c % 100, false),
            _ => null
        };
    }
}