I can't get value of base class field from child class object in c#

Question

using System;
public class Program
{
    public static void Main()

         CloudCollectionHelper cloudHelper = new CloudCollectionHelper();
         SlackHelper slackHelper = new SlackHelper();
        cloudHelper.DatabaseID=12345;
        Console.WriteLine(slackHelper.GetSlackPageTokens());
    }
    class CloudCollectionHelper
    {
        public  long DatabaseID { get; set; }
    }
    class SlackHelper:CloudCollectionHelper
    {

        public long GetSlackPageTokens()
        {
            return DatabaseID;
        }
    }
}

current output: 0 Expected Output: 12345

 

I need output 12345 because DatabaseID from the cloudhelper so i need that databaseID in the slackhelper.

 

this is my c# online compiler: https://dotnetfiddle.net/QNQeEX

 

I dont want to write something below because I have 1000+ field in the cloudhelper

SlackHelper slackHelper = new SlackHelper();
slackHelper.DatabaseID=12345;
Console.WriteLine(slackHelper.GetSlackPageTokens());

Thanks in advance.