using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var primarySellerId = 2;

        var mpKey = "|Amazon.com";

        var mpInfo = mpKey.Split('|');

        if (mpInfo.Length == 2)

        {

            var directMarketPlaceSellerId = FindDirectMarketPlaceSellerID(primarySellerId, mpInfo[1]);

            if (directMarketPlaceSellerId != null) {

                Console.WriteLine(directMarketPlaceSellerId);

            }

        }

    }

    public static int? FindDirectMarketPlaceSellerID(int primarySellerId, string marketPlaceSellerName) {

        if (DirectMarketPlaceSellerIdentifiers.Any(x => {return x.Equals(marketPlaceSellerName, StringComparison.InvariantCultureIgnoreCase);})) {

            return primarySellerId;

        } 

        return null;

    }

    private static readonly List<string> DirectMarketPlaceSellerIdentifiers = new List<string>()

    {

        "Amazon",

        "Amazon.com",

        "Amazon fulfillment"

        // Add all known other seller name variants

    };

}