Android : Creating fragments programatically android Xamarin

I am creating fragment in android Xamarin.

This is what I have done so far:-

PortfolioFragment.cs

class PortfolioFragment: Fragment
{
    public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
    {
        base.OnCreateView(inflater, container, savedInstanceState);

        var view = inflater.Inflate(Resource.Layout.portfolio_fragment, container, false);


        return view;
    }
}

fragment.axml

 <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:minWidth="25px"
    android:minHeight="25px">
    <TextView
        android:text="Large Text"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/textView1" />
</LinearLayout>

Main.cs

 PortfolioFragment pFragment = new PortfolioFragment();
      FragmentTransaction fragmentTx = this.FragmentManager.BeginTransaction().Replace(Resource.Id.fragment_container, pFragment);

But I receive an error:

Error   1   'MyProject.Resource.Id' does not contain a definition for 'fragment_container'  

What can be wrong?