asp.net core on filter empty fields are displayed

Question

I have filter implemented for WOStatus. When app run, it will display an emty field. Details below

 

[BindProperty(SupportsGet = true)]
        public string SearchWOStatus { get; set; }
        public async Task<IActionResult> OnGetAsync()
        {
            var userId = User.FindFirstValue(ClaimTypes.NameIdentifier);
            var orgid = await _context.UsersData.Where(s => s.Id == userId).Select(s => s.OrgID).FirstOrDefaultAsync();

            WOVL = await(from a in _context.WOMains.Where(s => s.OrgID == orgid)
                         join b in _context.WOInitiators on a.WOMainID equals b.WOMainID into Temp1
                         from c in Temp1.DefaultIfEmpty()
                         join d in _context.WOPlanners on a.WOMainID equals d.WOMainID into Temp2
                         from e in Temp2.DefaultIfEmpty()
                         select new WOViewIndex
                         {
                             WOMainID = a.WOMainID,
                             WONumber = a.WONumber,
                             WONumberS = e == null ? 0 : e.WONumberS,
                             CreateDate = a.CreateDate,
                             Deficiency = c.Deficiency,
                             Activity = e == null ? "--NONE--" : e.Activity,
                             WOStatus = e == null ? "--NONE--" : e.WOStatus
                         }).ToListAsync();

            return Page();
        }
        public async Task<IActionResult> OnPost(string SearchWOStatus)
        {
            var userId = User.FindFirstValue(ClaimTypes.NameIdentifier);
            var orgid = await _context.UsersData.Where(s => s.Id == userId).Select(s => s.OrgID).FirstOrDefaultAsync();
            if (SearchWOStatus != null)
            {
                WOVL = await (from a in _context.WOMains.Where(s => s.OrgID == orgid)
                              join b in _context.WOInitiators on a.WOMainID equals b.WOMainID into Temp1
                              from c in Temp1.DefaultIfEmpty()
                              join d in _context.WOPlanners.Where(s => s.WOStatus.Equals(SearchWOStatus)) on a.WOMainID equals d.WOMainID into Temp2
                              from e in Temp2.DefaultIfEmpty()
                              select new WOViewIndex
                              {
                                  WOMainID = a.WOMainID,
                                  WONumber = a.WONumber,
                                  WONumberS = e == null ? 0 : e.WONumberS,
                                  CreateDate = a.CreateDate,
                                  Deficiency = c.Deficiency,
                                  Activity = e == null ? "--NONE--" : e.Activity,
                                  WOStatus = e.WOStatus
                              }).ToListAsync();
            }

            return Page();
        }

<form method="post">
    <div class="row no-gutters">
        <div class="col-md-2 ml-2">
            <label class="form-control text-white" style="background-color:firebrick">Sort by WO Status</label>
        </div>
        <div class="col-md-2">
            <select id="woStatus" class="form-control" style="border-color:firebrick; color:firebrick" OnChange="assignData()">
                <option value="">--Select WO Status--</option>
                <option value="1">Initiated</option>
                <option value="2">Reviewed</option>
                <option value="3">Planned</option>
                <option value="4">Approved</option>
                <option value="5">Rejected</option>
                <option value="6">Scheduled</option>
                <option value="7">InProgress</option>
                <option value="8">Completed</option>
                <option value="9">Closed</option>
            </select>
            <input hidden asp-for="SearchWOStatus" id="WOStatusName" />
        </div>
        <div class="col-md-1 ml-1">
            <input class="btn btn-link" style="border-color:firebrick; color:firebrick; width:150px" type="submit" value="Filter by Status" />
        </div>
        <div class="col-md-1 ml-1">
            <a asp-route-page="/WO/Index" class="btn btn-link" style="border-color:firebrick; color:firebrick; width:150px">Show All</a>
        </div>
    </div>
</form>

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