不能强制转换为android.support.v4.app.片段(Xamarin c#)

我试着做DrawerLayout

但我面临的问题

Java.Lang.ClassCastException: tieit.droid.MyListFragment cannot be cast to android.support.v4.app.Fragment

这是我的代码在MainViewModel代码:

  using MvvmCross.Core.ViewModels;
using System;
using System.Collections.Generic;
namespace TieiT.Core
{
    public class MainViewModel : MvxViewModel
    {
        readonly Type[] _menuItemTypes = {
            typeof(MyListViewModel),
            typeof(MySettingsViewModel),
        };
        public IEnumerable<string> MenuItems { get; private set; } = new [] { "My List", "My Settings" };
        public void ShowDefaultMenuItem()
        {
            NavigateTo (0);
        }
        public void NavigateTo (int position)
        {
            ShowViewModel (_menuItemTypes [position]);
        }
    }
    public class MenuItem : Tuple<string, Type>
    {
        public MenuItem (string displayName, Type viewModelType)
            : base (displayName, viewModelType)
        {}
        public string DisplayName
        {
            get { return Item1; }
        }
        public Type ViewModelType
        {
            get { return Item2; }
        }
    }
}

当我有错误时，它会高亮显示:

public void NavigateTo (int position)
    {
        ShowViewModel (_menuItemTypes [position]);
    }

MyListFragment:

   using Android.OS;
using Android.Runtime;
using Android.Views;
using MvvmCross.Droid.Shared.Attributes;
using MvvmCross.Droid.FullFragging.Fragments;

using TieiT.Core;
namespace TieiT.Droid
{
    [MvxFragmentAttribute(typeof(MainViewModel), Resource.Id.frameLayout)]
    [Register("tieit.droid.MyListFragment")]
    public class MyListFragment : MvxFragment<MyListViewModel>
    {
        public override View OnCreateView (LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
        {
            return inflater.Inflate(Resource.Layout.MyListView, container, false);
        }
    }
}

这里是我需要显示DrawerLayout的活动:

 using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Android.App;
using Android.Content;
using Android.OS;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using MvvmCross.Droid.Support.V7.AppCompat;
using TieiT.Droid;
using Android.Support.V7.App;
using Android.Support.V4.Widget;
using Toolbar = Android.Support.V7.Widget.Toolbar;
using Fragment = Android.Support.V4.App.Fragment;
using TieiT.Core;
namespace TieiT.Droid.Views
{
    [Activity]
    public class GeneralInfo : MvxCachingFragmentCompatActivity<MainViewModel>
    {
        ActionBarDrawerToggle _drawerToggle;
        ListView _drawerListView;
        DrawerLayout _drawerLayout;
        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            SetContentView(Resource.Layout.GeneralInfoPage);
            var toolbar = FindViewById<Toolbar>(Resource.Id.toolbar);
           SetSupportActionBar(toolbar);
            SupportActionBar.SetDisplayHomeAsUpEnabled(false);
            _drawerListView = FindViewById<ListView>(Resource.Id.drawerListView);
            _drawerListView.ItemClick += (s, e) => ShowFragmentAt(e.Position);
            _drawerListView.Adapter = new ArrayAdapter<string>(this, global::Android.Resource.Layout.SimpleListItem1, ViewModel.MenuItems.ToArray());
            _drawerLayout = FindViewById<DrawerLayout>(Resource.Id.drawerLayout);
            _drawerToggle = new ActionBarDrawerToggle(this, _drawerLayout, Resource.String.OpenDrawerString, Resource.String.CloseDrawerString);
            _drawerLayout.SetDrawerListener(_drawerToggle);
            ShowFragmentAt(0);
        }
        void ShowFragmentAt(int position)
        {
            ViewModel.NavigateTo(position);
            Title = ViewModel.MenuItems.ElementAt(position);
            _drawerLayout.CloseDrawer(_drawerListView);
        }
        protected override void OnPostCreate(Bundle savedInstanceState)
        {
            _drawerToggle.SyncState();
            base.OnPostCreate(savedInstanceState);
        }
        public override bool OnOptionsItemSelected(IMenuItem item)
        {
            if (_drawerToggle.OnOptionsItemSelected(item))
                return true;
            return base.OnOptionsItemSelected(item);
        }
    }
}

如何修复这个错误?

谢谢你的帮助。

更新

My Main Layout:

    <?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/drawerLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
<!-- content must go before menu because of z-order -->
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">
        <include
            layout="@layout/toolbar" />
        <FrameLayout
            android:id="@+id/frameLayout"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    </LinearLayout>
<!-- menu -->
    <ListView
        android:id="@+id/drawerListView"
        android:layout_gravity="start"
        android:choiceMode="singleChoice"
        android:layout_width="240dp"
        android:layout_height="match_parent"
        android:background="?android:attr/windowBackground" />
</android.support.v4.widget.DrawerLayout>

下面是我在console中的内容:

    [ERROR] FATAL UNHANDLED EXCEPTION: Java.Lang.ClassCastException: tieit.droid.MyListFragment cannot be cast to android.support.v4.app.Fragment
10-01 19:52:15.838 E/mono-rt ( 3039):   --- End of managed Java.Lang.ClassCastException stack trace ---
10-01 19:52:15.838 E/mono-rt ( 3039): java.lang.ClassCastException: tieit.droid.MyListFragment cannot be cast to android.support.v4.app.Fragment