using System;
using System.Net;
using System.Net.Security;
using System.Security;
using System.Data;
using System.Collections.Generic;
using System.Linq;
using System.Text;


//using System.Windows.Forms;
using Microsoft.SharePoint.Client;

namespace OnlineDownLoadConsoleApp
{
    class Program
    {
        static void Main(string[] args)
        {
            //System.Net.ServicePointManager.SecurityProtocol = System.Net.SecurityProtocolType.Tls12;
            ServicePointManager.SecurityProtocol = (SecurityProtocolType)768 | (SecurityProtocolType)3072;
            DownloadOnlineFile();

        }



        public static void DownloadOnlineFile()
        {
            byte[] emptyBytes = new byte[0];
            string username = "account@domain.xyz";
            string password = "PASSWORD";
            string url = "https://xyz.sharepoint.com/sites/Sitename/Shared%20Documents/File.xlsx";
            string FilePath = "c:\\temp\\File.xlsx";
            var securedPassword = new SecureString();
            foreach (var c in password.ToCharArray()) securedPassword.AppendChar(c);
            var credentials = new SharePointOnlineCredentials(username, securedPassword);
            try
            {
                DownloadFile(url, credentials, FilePath);
            }
            catch (Exception ex)
            {
                Console.WriteLine("ex: " + ex.Message + "   Innerex:" + ex.InnerException.Message);
            }
        }

        private static void DownloadFile(string webUrl, ICredentials credentials, string fileRelativeUrl)
        {
            byte[] emptyBytes = new byte[0];

            try
            {
                using (var client = new WebClient())
                {
                    client.Headers.Add("X-FORMS_BASED_AUTH_ACCEPTED", "f");
                    client.Headers.Add("User-Agent: Other");
                    client.Credentials = credentials;

                    client.DownloadFile(webUrl, fileRelativeUrl);
                }
            }
            catch (Exception ex)
            {

                Console.WriteLine("ex: " + ex.Message + "   Innerex:" + ex.InnerException.Message);
            }
        }



    }
}