Generic CSOM code to call any version of SharePoint

static void Main(string[] args)
       {
           System.IO.StreamReader Sr = new System.IO.StreamReader(@"D:\Test\SitUrls.txt");
           System.IO.StreamWriter ErrorSw = new System.IO.StreamWriter(@"D:\Test\ErrorLog.txt");
           System.IO.StreamWriter Sw = new System.IO.StreamWriter(@"D:\Test\Owner.csv");
           Sw.WriteLine("Site Url, Group Name, User Name, User Email");

           while (!Sr.EndOfStream)
           {
               var urlsdetail = Sr.ReadLine();
               string[] urldetails = urlsdetail.Split(';');

               var url = urldetails[0];
               var type = urldetails[1];

               url = url.Trim();
               using (ClientContext clientContext = new ClientContext(url))
               {

                   Web oWebsite = clientContext.Web;
                   string web;
                   if(type.ToLower()=="online")
                   {
                        var login = "[email protected]";
                       var password = "XXXXX";
                       var securePassword = new SecureString();
                       foreach (char c in password)
                       { securePassword.AppendChar(c); }
                       var onlineCredentials = new SharePointOnlineCredentials(login, securePassword);

                       clientContext.Credentials = onlineCredentials;
                       web = url;

                   }

                   clientContext.Load(oWebsite, website => website.Title, website => website.Lists, website => website.ServerRelativeUrl);
                   clientContext.ExecuteQuery();

                   Microsoft.SharePoint.Client.GroupCollection groupColl = oWebsite.SiteGroups;
                   clientContext.Load(groupColl, groups => groups.Include(group => group.Title, group => group.Id));
                   clientContext.ExecuteQuery();
                   foreach (Microsoft.SharePoint.Client.Group siteGroup in groupColl)
                   {
                       string groupName = siteGroup.Title;

                           UserCollection usersColl = siteGroup.Users;
                           clientContext.Load(usersColl, users => users.Include(user => user.Title, user => user.Email));
                           clientContext.ExecuteQuery();

                           foreach (User user in usersColl)
                           {
                               string userName = user.Title;
                               string email = user.Email;
                               Sw.WriteLine("\"" + urlsdetail + "\"," + "\"" + groupName + "\"," + "\"" + userName + "\"," + "\"" + email + "\"");
                           }
                   }
               }
           }
           Sw.Close();
           ErrorSw.Close();
           Console.WriteLine("Executed Successfully");