我收到此错误（System.Web.Mvc.WebViewPage <tmodel> .Model.get返回空。）

Question

Home Controller 
public ActionResult Index()
{
    MenuModel ObjMenuModel = new MenuModel();
    ObjMenuModel.MainMenuModel = new List<MainMenu>();
    ObjMenuModel.MainMenuModel = GetMainMenu();
    ObjMenuModel.SubMenuModel = new List<SubMenu>();
    ObjMenuModel.SubMenuModel = GetSubMenu();

    return View(ObjMenuModel);
}

public List<MainMenu> GetMainMenu()
{
    List<MainMenu> ObjMainMenu = new List<MainMenu>();
    ObjMainMenu.Add(new MainMenu { ID = 1, MainMenuItem = "Home", MainMenuURL = "#" });
    ObjMainMenu.Add(new MainMenu { ID = 2, MainMenuItem = "System Setup", MainMenuURL = "#" });
    return ObjMainMenu;
}

public List<SubMenu> GetSubMenu()
{
    List<SubMenu> ObjSubMenu = new List<SubMenu>();
    ObjSubMenu.Add(new SubMenu { MainMenuID = 2, SubMenuItem = "Customer Information", SubMenuURL= "Employer" });
    ObjSubMenu.Add(new SubMenu { MainMenuID = 2, SubMenuItem = "Chart Of Accounts", SubMenuURL = "CompanyProfile" });
    return ObjSubMenu;
}

My Model
namespace Ron_Financial_Management_System.Models
{
    public class MenuModel
    {
        public List<MainMenu> MainMenuModel { get; set; }
        public List<SubMenu> SubMenuModel { get; set; }
    }

    public class MainMenu
    {
        public int ID;
        public string MainMenuItem;
        public string MainMenuURL;
    }

    public class SubMenu
    {
        public int MainMenuID;
        public string SubMenuItem;
        public string SubMenuURL;
    }
}

错误发生在行

foreach (var MenuItem in Model.MainMenuModel)

在我看来。

我得到的错误：

  

System.Web.Mvc.WebViewPage.Model.get返回null。

有人可以帮助我解决可能的问题吗？