Disable Entity Framework validation for some specific field on insertion action

I am trying to disable validation of some field including password while inserting data. But I am getting the following error while inserting:

Cannot insert the value NULL into column 'Password', table 'Uni.Models.MyDb.dbo.Students'; column does not allow nulls. INSERT fails. The statement has been terminated.

My model class:

public class Student
{
    [Key]
    public int StudentId { get; set; }

    [Required(ErrorMessage = "Name Required")]
    public string Name { get; set; }

    public string IdNumber { get; set; }

    [Required(ErrorMessage = "Please Enter Password"), MinLength(5, ErrorMessage = "Password length error")]
    public string Password { get; set; }

    [Required, Compare("Password", ErrorMessage = "Invalid Confirm Password")]
    public string ConfirmPassword { get; set; }

    [Required(ErrorMessage = "Date Of Birth Required")]
    [Column(TypeName = "Date")]
    public DateTime BirthDate { get; set; }


    public virtual Gender Gender { get; set; }
    [Required(ErrorMessage = "Select Gender!")]
    public int GenderId { get; set; }
}

My controller:

[HttpPost]
[ValidateAntiForgeryToken]
[AllowAnonymous]
public ActionResult add(Student std)
{
    db.Configuration.ValidateOnSaveEnabled = false;

    if (ModelState.IsValidField("Name") && ModelState.IsValidField("GenderId") && ModelState.IsValidField("BirthDate"))
    {
        Common common = new Common();
        std.IdNumber = common.generateUsername("S-");

        db.Students.Add(std);

        db.SaveChanges();
        db.Configuration.ValidateOnSaveEnabled = true;

        return RedirectToAction("Index");
    }

    ViewBag.Genders = new SelectList(db.Genders, "GenderId", "Dari");
    ViewBag.Provinces = new SelectList(db.Provinces, "ProvinceId", "Name");

    return View();
}

I really appreciate anyone could help me with this and tell me where am I going wrong.