getting actionbar null in my xamarin.andoird application - android-activity

Question

I am new to xamarin.android native. i am learning and developing this app from this tutorial
Tutorial Video link
but i am getting nullreference exception beacuse my actionbar is null.tutorial auther shared source code also.i ahve done same still its not working in my app.
this is my code:
MainMenuPage.axml
<?xml version="1.0" encoding="utf-8"?> <LinearLayoutxmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<FrameLayout
android:id="#+id/fragmentContainer"
android:layout_height="match_parent"
android:layout_width="match_parent" />
</LinearLayout>
MainActivity.cs
[Activity(Label = "HotDogMenuActivityWithTabs",Icon = "#drawable/smallicon",Theme = "#style/AppTheme")]
public class HotDogMenuActivityWithTabs : Activity
{
private ListView hotDogListView;
private List<HotDog> allHotDogs;
private HotDogDataService hotDogDataService;
protected override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
ActionBar.NavigationMode = ActionBarNavigationMode.Tabs;
AddTab("Favorites", Resource.Drawable.FavoritesIcon, new FavoriteHotDogFragment());
AddTab("Meat Lovers", Resource.Drawable.MeatLoversIcon, new MeatLoversFragment());
AddTab("Veggie Lovers", Resource.Drawable.veggieloversicon, new VeggieLoversFragment());
}
private void AddTab(string tabText, int iconResourceId, Fragment view)
{
var tab = this.ActionBar.NewTab();
tab.SetText(tabText);
tab.SetIcon(iconResourceId);//TODO
tab.TabSelected += delegate (object sender, Android.App.ActionBar.TabEventArgs e)
{
var fragment = this.FragmentManager.FindFragmentById(Resource.Id.fragmentContainer);
if (fragment != null)
e.FragmentTransaction.Remove(fragment);
e.FragmentTransaction.Add(Resource.Id.fragmentContainer, view);
};
tab.TabUnselected += delegate (object sender, Android.App.ActionBar.TabEventArgs e)
{
e.FragmentTransaction.Remove(view);
};
this.ActionBar.AddTab(tab);
}
protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
{
base.OnActivityResult(requestCode, resultCode, data);
if (resultCode == Result.Ok && requestCode == 100)
{
var selectedHotDog = hotDogDataService.GetHotDogById(data.GetIntExtra("selectedHotDogId", 0));
var dialog = new Android.App.AlertDialog.Builder(this);
dialog.SetTitle("Confirmation");
dialog.SetMessage(string.Format("You've added {0} time(s) the {1}", data.GetIntExtra("amount", 0), selectedHotDog.Name));
dialog.Show();
}
}
}
Style.xaml
<resources>
<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar" >
<!-- Customize your theme here. -->
<item name="colorPrimary">#color/colorPrimary</item>
<item name="colorPrimaryDark">#color/colorPrimaryDark</item>
<item name="colorAccent">#color/colorAccent</item>
</style>
what is wrong i am doing here.please help
tahnkx in advance.