using System;

using System.Runtime.CompilerServices;

using System.Globalization;

​

public class Program

{

    [InterpolatedStringHandler]

    public ref struct HardcodedCultureHandler

    {

        private DefaultInterpolatedStringHandler _wrapped;

​

        public HardcodedCultureHandler(int literalLength, int formattedCount)

        {

            _wrapped = new(literalLength, formattedCount, CultureInfo.GetCultureInfo("ar-SA"));

        }

​

        public void AppendLiteral(string s) => _wrapped.AppendLiteral(s);

        public void AppendFormatted<T>(T t) => _wrapped.AppendFormatted(t);

        public void AppendFormatted<T>(T t, string format) => _wrapped.AppendFormatted(t, format);

        public string ToStringAndClear() => _wrapped.ToStringAndClear();

    }

    public static void Main()

    {

        DateTime? x = DateTime.Now.AddMonths(2);

        Console.WriteLine(string.Create(CultureInfo.GetCultureInfo("ar-SA"), $"{x:dd MMM yyy}"));

        Console.WriteLine(SameCodeAsStringCreate(CultureInfo.GetCultureInfo("ar-SA"), $"{x:dd MMM yyy}"));

        Console.WriteLine(HardcodedCulture($"{x:dd MMM yyy}"));

    }

    // We have to pass culture as another argument to this function,

    // so it can be used in the code generated for creation of the handler

    private static string SameCodeAsStringCreate(IFormatProvider provider, [InterpolatedStringHandlerArgument(nameof(provider))] DefaultInterpolatedStringHandler interpolatedString) =>

        interpolatedString.ToStringAndClear();

    private static string HardcodedCulture(HardcodedCultureHandler interpolatedString) => interpolatedString.ToStringAndClear();

​

}