问值为空值的IQueryable

EN

IQueryable<PetTable> petIQ= from s in _context.PetT select s;
    if (!String.IsNullOrEmpty(searchString))
        {
            petIQ = _context.PetT
                .Where(x => x.PetName.ToString() == searchString)
                    .Select(s => new PetTable
                        {
                             PetName = s.PetName,
                             PetAddress = s.PetAddress,
                             PetIDTag = s.PetIDTag.Where(x => s.PetIDTag != null)
                        });
        }