using System;

using System.Collections;

using System.Linq;

​

class Program

{

    static void Main(string[] args)

    {

        object obj = new int[] {1,2,3};

        string result = ObjectToString(obj);

        Console.WriteLine(result);

    }

​

    public static string ObjectToString(object? obj)

    {

        if (obj is IEnumerable enumerable)

        {

            return string.Join(",", enumerable.Cast<Object>()); 

        }

        return obj?.ToString() ?? "<unknown>";

    }

}