String Interpolation with IFormattable

IFormattableStringInterpolation.cs

private static readonly IEnumerable<string> Cultures = new[] { "en-us", "fr", "zh-hk", "ja-jp" };

public static void Y()
{
    var x = 10;

    IFormattable f = $"{x :c}, {x :n}";

    foreach (var c in Cultures)
    {
        var s = WithCulture(f, c);
        Console.WriteLine(s);
    }
}

public static void SameAsY()
{
    var x = 10;

    IFormattable f = System.Runtime.CompilerServices.FormattableStringFactory.Create("{0:c}, {1:n}", x, x);

    foreach (var c in Cultures)
    {
        var s = WithCulture(f, c);
        Console.WriteLine(s);
    }
}

private static string WithCulture(IFormattable f, string cultureName)
{
    return f.ToString(null, System.Globalization.CultureInfo.CreateSpecificCulture(cultureName));
}