public ActionResult Index(string searchString)
        {

            IEnumerable<HotelAvailability> hotels = db.HotelAvailabilities.Include(c => c.Hotel);

            if (!String.IsNullOrEmpty(searchString))
            {
                hotels = db.HotelAvailabilities.Include(c => c.Hotel).Where(
                    s => s.RoomType.Contains(searchString) || s.AvailabilityDate.Equals(searchString) ||

                    s.Hotel.HotelName.Contains(searchString));
                return View(hotels);
            }

<div class="box-tools pull-right">
                       @using (Html.BeginForm("Index", "HotelAvailabilities", FormMethod.Get))
                       {
                            <div class="input-group" style="width: 150px;">
                                <input type="text" name="searchString" class="form-control input-sm pull-right" placeholder="Search">
                                <div class="input-group-btn">
                                    <button class="btn btn-sm btn-success"><i class="fa fa-search"></i></button>
                                </div>
                            </div>
                        }
                    </div>