using System;

​

//https://stackoverflow.com/questions/71546789/the-u-escape-sequence-in-c-sharp

public class Program

{

    public static void Main()

    {

        // These compile because they're valid Hex numbers in the range 000000 - 10FFFF padded to 8 digits with leading zeros:

        Console.WriteLine("\U0001F47D");

        Console.WriteLine("\U00000000");

        Console.WriteLine("\U0010FFFF");

        // But these don't.

        // H is not a valid Hex character:

        // Compilation error (line 16, col 22): Unrecognized escape sequence

        Console.WriteLine("\U00HHHHHH");

        // This is outside the range of 000000 - 10FFFF:

        // Compilation error (line 19, col 22): Unrecognized escape sequence

        Console.WriteLine("\U001effff");

    }

}

​