Hi Everyone, Help please!

This is an accessibility question, and I can't seem to figure out the best way to go about it.
I want to set a variable that is bound to an entity (label.text in this case) in my OnAppearing method. i.e. I want to set the label when the page is loaded.

I've got my xaml page:

<?xml version="1.0" encoding="utf-8" ?>
...

         xmlns:local="clr-namespace:App13"
         x:Class="App13.MainPage">

<ContentPage.BindingContext>
    <local:myViewModel />
</ContentPage.BindingContext>

<StackLayout>

    <Label Text="{Binding myBindingEntry}" 

       HorizontalOptions="Center"
       VerticalOptions="CenterAndExpand" />

    <Button Text="Command Button"
            Command="{Binding btnCommand}"
            HorizontalOptions="Center"
            VerticalOptions="CenterAndExpand"
            />

</StackLayout>

'

And I've created another file, called myViewModel.cs :


using System.ComponentModel;
using System.Windows.Input;
using Xamarin.Forms;

namespace App13
{
class myViewModel : INotifyPropertyChanged
{

    string _myBindingEntry = "nothing!";

    public event PropertyChangedEventHandler PropertyChanged;
    public ICommand btnCommand { private set; get; }

    public myViewModel()
    {

        btnCommand = new Command(
            execute: () =>
            {
                myBindingEntry = "You have clicked the Command Button!";
                RefreshCanExecutes();
            }
            );


    }

    void RefreshCanExecutes()
    {
        ((Command)btnCommand).ChangeCanExecute();

    }

    public string myBindingEntry
    {

        private set
        {
            if (_myBindingEntry != value)
            {
                _myBindingEntry = value;
                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("myBindingEntry"));
            }
        }
        get
        {
            return _myBindingEntry;
        }


    }

}

}

And here's my code behind, which is where I want to set myBindingEntry:


using System.ComponentModel;
using Xamarin.Forms;

namespace App13
{
[DesignTimeVisible(false)]
public partial class MainPage : ContentPage
{
// I've tried declaring an instance of myViewModel class, to use later:
myViewModel fmyViewModel = new myViewModel();
public MainPage()
{
InitializeComponent();

    }

    protected override void OnAppearing()
    {

        // here is where I want to set the text of my Label.
        // i should be able to do it by assigning text to myBindingEntry

        // This generates 'The name 'myBindingEntry' does not exist in the current context.
        myBindingEntry = "this is set during OnAppearing";

        // or if I use this, I get:
        // Error CS0272  The property or indexer 'myViewModel.myBindingEntry' cannot be used in this context because the set accessor is inaccessible App13
        fmyViewModel.myBindingEntry = "using an instance of the view model!"

        base.OnAppearing();
    }

}

}