asp.mvc 4 EF ActionResult Edit with not all fields in view
[HttpPost]
public ActionResult Edit(User user)
{
  if (ModelState.IsValid)
  {
    db.Entry(user).State = EntityState.Modified;
    db.SaveChanges();
    return RedirectToAction("Index");
  }
 return View(user);
}

[HttpPost]
public ActionResult Edit(user user)
{
    user v = db.Users.Find(user.ID);
    ModelState.Remove("Pass");


    user.Password = v.Password;           // assign from db

    if (ModelState.IsValid)
    {

        //db.Entry(user).State = EntityState.Modified; // this won't work as the context changed
        db.Entry(v).CurrentValues.SetValues(user); // we need to use this now
        db.SaveChanges();
        return RedirectToAction("Index");
    }
    return View(user);
}

if (ModelState.IsValid)

if (string.IsNullOrEmpty(user.Password))
{
    ModelState.Remove("Password");
}

public class UserModel
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string Surname { get; set; }
}

[HttpPost]
public ActionResult Edit(UserModel userModel)
{

    if (ModelState.IsValid)
    {
        User user = db.Users.Find(userModel.Id);
        user.FirstName = userModel.FirstName ;
        user.Surname  = userModel.Surname;
        db.SaveChanges();
        return RedirectToAction("Index");
    }
    return View(userModel);
}