Fix the following Error Operator '&&' cannot be applied to operands of type 'System.Linq.IQueryable<>' and 'lambda expression'

Watch this example on YouTube:
 



Replace 

      public ActionResult TestPage(TESTEntities model = null)
        {
            var test = (from z in model.Customers2
                        select z);
            if (!String.IsNullOrEmpty(model.Customers2.First().CustomerFirstName))
            {
                test = model.Customers2.Where(s => s.CustomerFirstName != null) &&
                   (s => s.FirstOrDefault().ToString().Trim().Equals(model.Customers2.FirstOrDefault().CustomerFirstName.Trim()));
            }
            return View();
        }

With 

      public ActionResult TestPage(TESTEntities model = null)
        {
            var test = (from z in model.Customers2
                        select z);
            if (!String.IsNullOrEmpty(model.Customers2.First().CustomerFirstName))
            {
                //test = model.Customers2.Where(s => s.CustomerFirstName != null) &&
                 //   (s => s.FirstOrDefault().ToString().Trim().Equals(model.Customers2.FirstOrDefault().CustomerFirstName.Trim()));
                test = model.Customers2.Where(s => s.CustomerFirstName == null ? false : s.CustomerFirstName.Equals("AAA"));
            }
            return View();
        }