using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var foo = "foo";

        var bar = "bar";

        var field = new Dictionary<string,string> {{ "1", "foo|bar" }};

        var fieldList = field.ToList();

        var truth = fieldList.FirstOrDefault(x=>x.Value.Contains(foo + bar));

        if (truth.Key == null){

          Console.WriteLine("not found");

        }

​

        Console.WriteLine(truth.Key);               

        Console.WriteLine(truth.Value);

    }

}