Android Xamarin - FindViewById returns all except the top LinearLayout

Question

Using Xamarin.Android native in Visual Studio 2017.

Here is an example of my layout. Let's call it 'headache.axml'.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/topLinearLayoutId"
    android:paddingLeft="20dp"
    android:paddingTop="0dp"
    android:paddingRight="20dp"
    android:paddingBottom="15dp"
    android:layout_height="0dp"
    android:layout_weight="1"
    android:layout_width="match_parent"
    android:onClick="showPasswordDialog"
    android:orientation="horizontal" >

     <TextView  android:id="@+id/sampleId_0"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"/>

     <TextView  android:id="@+id/sampleId_1"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"/>

     . . . more views . . .

    </LinearLayout>

And here is the code where I inflate this layout.

View view = inflater.Inflate(Resource.Layout.fragment_selection, container, false);
ViewStub stub = (ViewStub) view.FindViewById(stubIds[i]);
stub.LayoutResource = Resource.Layout.headache;
View inflatedView = stub.Inflate();

Then I can use inflatedView.FindViewById() to get any view from my layout except the top LinearLayout. For example, these lines work perfect:

var txtView0 = (TextView) inflatedView.FindViewById(Resource.Id.sampleId_0);
var txtView1 = (TextView) inflatedView.FindViewById(Resource.Id.sampleId_1);

Both txtView0 and txtView1 are initialized.

And here is my problem, when I try to get the top View from my layout I get null:

var top = (LinearLayout) inflatedView.FindViewById(Resource.Id.topLinearLayoutId); // returns null

---

As a workaround,

I've added a pre-top LinearLayout to my 'headache.axml'. It's become like this:

<?xml version="1.0" encoding="utf-8"?>
<!-- workaround: pre-top LinearLayout (still inaccessible) -->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/glitchyLinearLayout"
android:layout_height="match_parent"
android:layout_width="match_parent"
android:orientation="horizontal">

<!-- workaround: accessible LinearLayout -->
<LinearLayout
    android:id="@+id/topLinearLayoutId"
    android:paddingLeft="20dp"
    android:paddingTop="0dp"
    android:paddingRight="20dp"
    android:paddingBottom="15dp"
    android:layout_height="0dp"
    android:layout_weight="1"
    android:layout_width="match_parent"
    android:orientation="vertical">

     <TextView  android:id="@+id/sampleId_0"
                ... all the same ... />

     <TextView  android:id="@+id/sampleId_1"
                ... all the same ... />

     . . . more views . . .

    </LinearLayout>

Now I can get my topLinearLayoutId.

var top = (LinearLayout) inflatedView.FindViewById(Resource.Id.topLinearLayoutId);

In this case, the top is initialized and my application works well.

But I'd like to understand why the hell I've got this problem.