Drop down lis and search in MVC # database first

Question

I'm begginer and This my First Large MVC3 App using Entity Framework Model.
This is a image of the .EDMX Model that I am using


I create Candidate and Skill Controler,strongli tipe view for edit, detail, and delete.

  public class CandidateController : Controller
  {
  private Models.CandidatEntities data;
  public CandidateController()
  {
  data = new CandidatEntities();
  }

  public ActionResult Index()
  {
  var candidates = data.Candidate.ToList();
  return View(candidates);
  }
  public ActionResult Create()
  {
  return View();
  }
  [HttpPost]
  public ActionResult Create(Candidate candidate)
  {
  if (!ModelState.IsValid)
  {
  return View(candidate);
  }
  data.Candidate.AddObject(candidate);
  data.SaveChanges();
  return RedirectToAction("Index");
  }
  public ActionResult Details(int id)
  {
  var candidate = data.Candidate.Where(c => c.CandidateID == id).First();
  return View(candidate);
  }
  public ActionResult Edit(int id)
  {
  var candidate = data.Candidate.Where(c => c.CandidateID == id).First();
  return View(candidate);
  }
  [HttpPost]
  public ActionResult Edit(Candidate candidate)
  {
  var candidateToEdit = data.Candidate.Where(c => c.CandidateID == candidate.CandidateID).First();
  candidateToEdit.FirstName = candidate.FirstName;
  candidateToEdit.LastName = candidate.LastName;
  candidateToEdit.Email = candidate.Email;
  data.SaveChanges();
  return RedirectToAction("Index");
  }

  public ActionResult Delete(int id)
  {
  var candidate = data.Candidate.Where(c => c.CandidateID == id).First();
  return View(candidate);
  }

 [HttpPost]
  public ActionResult Delete(Candidate candidate)
  {
  var candidateToDelete = data.Candidate.Where(c => c.CandidateID == candidate.CandidateID).First();
 
  data.DeleteObject(candidateToDelete.FirstName);
  data.DeleteObject(candidateToDelete.LastName);
  data.DeleteObject(candidateToDelete.Email);
  data.SaveChanges();
  return RedirectToAction("Index");
  }
For this method I have problem:
  Sequence contains no elements

I need to add drop down list for skill and add a text box for entering a skillLevel and a button search wich return list of candidate for selected Skill and skillLevel.
I really do appriciate for any help.