值不能为空。来自viewdown中的dropdownfor viewbag警报

Question

我正在尝试使用下拉列表向数据库插入值。下拉列表中的值可以将完成的所有数据插入数据库。但它仍然在View中警告错误。

  

值不能为空

 @Html.DropDownListFor(Model => Model.JCY_SEC, new SelectList(ViewBag.Names as System.Collections.IEnumerable, "SECID", "SecTH"), "Select a Section")  

这是我的控制器

[HttpGet]
public ActionResult EmployeeView()
{
    ViewBag.Names = db.HRset_Section.ToList();
    return View();
}

这是我的插入方法

public ActionResult EmployeeView(EMPJCYMODEL customer, FormCollection collection)
{
    string constr = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {
        string query = "INSERT INTO HR_EMPLOYEE(JCY_EMPNO, JCY_EMP_NAME,JCY_EMP_SUR,st_date,JCY_SEC) VALUES(@JCY_EMPNO, @JCY_EMP_NAME,@JCY_EMP_SUR,@st_date,@JCY_SEC)";
        query += " SELECT SCOPE_IDENTITY()";
        using (SqlCommand cmd = new SqlCommand(query))
        {
            cmd.Connection = con;
            con.Open();
            cmd.Parameters.AddWithValue("@JCY_EMPNO", customer.JCY_EMPNO);
            cmd.Parameters.AddWithValue("@JCY_EMP_NAME", customer.JCY_EMP_NAME);
            cmd.Parameters.AddWithValue("@JCY_EMP_SUR", customer.JCY_EMP_SUR);
            cmd.Parameters.AddWithValue("@st_date", customer.st_date);
            cmd.Parameters.AddWithValue("@JCY_SEC", customer.JCY_SEC);
            customer.JCY_EMPNO = cmd.ExecuteScalar().ToString();
            con.Close();
        }
    }
    return View(customer);
}