Xamarin.Android : CS0103 The name 'SetSupportActionBar' does not exist in the current context

CS0103 The name 'SetSupportActionBar' does not exist in the current context

Am clean and build many of time but this error is occur and i will change my manifest xml theme also but there is an error how to can solve this issue

my android target platform api 27 and minimum 18

my mainactivity.cs only the error is occur how to solve this issue

i will find some answers from stackoverflow but it not solving my issue

MainActivity.cs

using System;
using Android.App;
using Android.Content;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;
using Android.Support.V7.App;
using Android.Support.V4.Widget;
using V7Toolbar = Android.Support.V7.Widget.Toolbar;
using Android.Support.Design.Widget;

namespace NavigationDrawerLayout
{
    [Activity(Label = "NavigationDrawerLayout", Theme = "@style/Theme.DesignDemo", MainLauncher = true, Icon = "@drawable/icon")]
    public class MainActivity : AppCompatActivity
    {

        DrawerLayout drawerLayout;
        NavigationView navigationView;
        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);

            // Set our view from the "main" layout resource
            SetContentView(Resource.Layout.Main);

            drawerLayout = FindViewById<DrawerLayout>(Resource.Id.drawer_layout);


            // Create ActionBarDrawerToggle button and add it to the toolbar
            var toolbar = FindViewById<V7Toolbar>(Resource.Id.toolbar);
            SetSupportActionBar(toolbar);


            var drawerToggle = new ActionBarDrawerToggle(this, drawerLayout, toolbar, Resource.String.drawer_open, Resource.String.drawer_close);
            drawerLayout.SetDrawerListener(drawerToggle);
            drawerToggle.SyncState();

            navigationView = FindViewById<NavigationView>(Resource.Id.nav_view);
            setupDrawerContent(navigationView);
        }
        void setupDrawerContent(NavigationView navigationView)
        {
            navigationView.NavigationItemSelected += (sender, e) => {
                e.MenuItem.SetChecked(true);
                drawerLayout.CloseDrawers();
            };
        }

        public override bool OnCreateOptionsMenu(IMenu menu)
        {

            navigationView.InflateMenu(Resource.Menu.nav_menu);
            return true;

        }

        }
}

toolbar.axml

 <?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/main_content"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.design.widget.AppBarLayout
android:id="@+id/appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:elevation="4dp"
android:background="?attr/colorPrimary" />
</android.support.design.widget.AppBarLayout>
</android.support.design.widget.CoordinatorLayout>
`

styles.xml

<?xml version="1.0" encoding="utf-8" ?>
<resources>
  <style name="Theme.DesignDemo" parent="Base.Theme.DesignDemo"></style>
  <style name="Base.Theme.DesignDemo" parent="Theme.AppCompat.Light.NoActionBar">
    <item name="colorPrimary">#2196F3</item>
    <item name="colorPrimaryDark">#1976D2</item>
    <item name="android:windowBackground">@color/window_background</item>
  </style>
</resources>

Change the class Activity into AppCompatActivity.

Then restart your Visual Studio.