using System;

using System.Linq;

​

public class Program

{

    readonly static (double lng, double lat)[] Locations = 

    {

        (10.757938, 52.437444),

        (10.764379, 52.437314),

        (10.770562, 52.439067),

        (10.773268, 52.436633),

    };

    public static void Main()

    {

        System.Threading.Thread.CurrentThread.CurrentCulture = new System.Globalization.CultureInfo("de-DE");

        string lngLats = Locations.Aggregate(string.Empty, (str, next) => str + $"{next.Item1:F6},{next.Item2:F6};");

        Console.WriteLine($"lngLats: {lngLats}\n");

        double x = 12.3456;

        string result = x.ToString(System.Globalization.CultureInfo.InvariantCulture);

        Console.WriteLine($"A double value: {result}\n");

    }

}