using System;

using System.Net;

using System.IO;

​

public class Program

{

    public static void Main()

    {

        var url = @"https://firebasestorage.googleapis.com/v0/b/oig-nasa-gov.appspot.com/o/data%2FMobileData.json?alt=media";

        //url = "https://oig.nasa.gov/MobileAppData.js";  // alternate server

        var request = WebRequest.CreateHttp(url);

        request.IfModifiedSince = new DateTime(2019, 7, 16, 0, 0, 0);  // set day 16 load, day = 17 no load

        try

        {

            var response = (HttpWebResponse)request.GetResponse();

            Show(response);

        }

        catch (WebException e)

        {

            Show((HttpWebResponse)e.Response);

        }

    }

​

    static void Show(HttpWebResponse response)

    {

        var code = (int)response.StatusCode; // 200,304,400, etc

        Console.WriteLine("Status: " + code + ": " + response.StatusDescription);

        Console.WriteLine("Last-Modified: " + response.Headers["Last-Modified"]);

        Console.WriteLine("Expires: " + response.Headers["Expires"]);

        Console.WriteLine("Content-Length: " + response.Headers["Content-Length"]);

        if (code == 200)

        {

            var json = new StreamReader(response.GetResponseStream()).ReadToEnd();

            Console.WriteLine("Json Data:\n" + json);

        }

        else if (code == 304)

        { // unmodified

            Console.WriteLine("Use locally cached copy of data.");

        }

    }

}