using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var data = new Dictionary<string, List<string>>();

        data.Add("Id", new List<string> { "3", "5", "3" });

        data.Add("Name", new List<string> { "A", "B", "C" });

        //var a = data["Id"].FindIndex(b => b == "3");

        int[] indexs = data["Id"].Select((b,i) => b == "3" ? i : -1).Where(i => i != -1).ToArray();

        foreach(var index in indexs)

        {

            Console.WriteLine(data["Name"][Convert.ToInt16(index)]);

        }   

    }

}