using System;

public class Program

{

    public static void Main()

    {

        // Id of the Contact in the format xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

        string contactId = "564bf874-7187-9c41-b947-2b2e93fe4ce7";

        var guid = Guid.Parse(contactId);

        var bytes = guid.ToByteArray();

        var encodedId = Convert.ToBase64String(bytes);

        Console.WriteLine("Contact Id:");

        Console.WriteLine(guid);

        Console.WriteLine();

        Console.WriteLine("Converted contact Id:");

        Console.WriteLine(encodedId);

        Console.WriteLine();

        Console.WriteLine("Robomongo query:");

        Console.WriteLine("db.getCollection('Contacts').find({" + string.Format("_id:new BinData(3, '{0}')", encodedId) + "})");

        Console.WriteLine();

        string base64contactId = "dPhLVodxQZy5Rysuk/5M5w==";

        Console.WriteLine("Parsing Base64 string:");

        Console.WriteLine(base64contactId);

        Console.WriteLine();

        Console.WriteLine("Into GUID:");

        Console.WriteLine(new Guid(Convert.FromBase64String(base64contactId)));

    }

}