using System;

using System.Collections.Generic;           

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        string LogInIDs = "124,345,876|765,322,98|565,99";

        Console.WriteLine(string.Join("\n", RetrieveAffCodes(LogInIDs, "322")));

        Console.WriteLine(string.Join("\n", RetrieveAffCodes(LogInIDs, "32")));

    }

    public static IEnumerable<string> RetrieveAffCodes(string logInIDs , string logInID)

    {

        //We split the list

        var list = logInIDs.Split('|');

        //We look for an item with the logInID, if found (?) we split using ',' and then we remove the item

        var match = list

            .Select(i => i.Split(',').Select(item => item.Trim()))

            .FirstOrDefault(i => i.Contains(logInID))?

            .Where(i => i != logInID);

        if(match != null)

        {

            return match;

        }

        return new List<string>();

    }

}

​