using System;

public class Program

{

    public static void Main()

    {

        Order orderInfo = null;

        var countryId = orderInfo?.CountryFromId != 0 ? orderInfo.CountryFromId : GetCurrentAgentFromCountryId();    

        Console.WriteLine(countryId);

    }

    public static int GetCurrentAgentFromCountryId()

    {

        return 5;

    }

    public class Order 

    {

        public int CountryFromId {get;set;}

    }

}