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

using System;

namespace MapControl;

public class UriTileSource : TileSource
{
    private string uriFormat;

    public string UriTemplate
    {
        get;
        set
        {
            field = value;
            uriFormat = field
                .Replace("{z}", "{0}")
                .Replace("{x}", "{1}")
                .Replace("{y}", "{2}")
                .Replace("{s}", "{3}");

            if (Subdomains == null && field.Contains("{s}"))
            {
                Subdomains = ["a", "b", "c"]; // default OpenStreetMap subdomains
            }
        }
    }

    public string[] Subdomains { get; set; }

    public override Uri GetUri(int zoomLevel, int column, int row)
    {
        Uri uri = null;

        if (uriFormat != null)
        {
            var uriString = Subdomains?.Length > 0
                ? string.Format(uriFormat, zoomLevel, column, row, Subdomains[(column + row) % Subdomains.Length])
                : string.Format(uriFormat, zoomLevel, column, row);

            uri = new Uri(uriString, UriKind.RelativeOrAbsolute);
        }

        return uri;
    }
}

public class TmsTileSource : UriTileSource
{
    public override Uri GetUri(int zoomLevel, int column, int row)
    {
        return base.GetUri(zoomLevel, column, (1 << zoomLevel) - 1 - row);
    }
}