How do i solve this strange error in my .Net MAUI page?

Trying to learn MAUI i prepare a page where there is a Label that is hidden. At a certain event the label becomes visible. All it works ok, but when i put this label inside a "CollectionView" trying to bind her with a value from a database the Label become "not existing in the current context" with the error shown in this picture. Where is the error that i made? Thanks!

The XAML Page with the CollectionView is this :

Yes,you cannot reference item inside a template by x:Name. You can use data binding to control templated UI elements from your ViewModel, just as Jason said.

Based on your code, I created a demo and achieved this function.

You can refer to the following code:

1.try to add a new property IsVisible to your Item model, and bind it to your Label Matr. And you also need to implement interface INotifyPropertyChanged for your Item, if you change the value of item's property IsVisible, the UI will refresh automatically.

public class Item: INotifyPropertyChanged 
{
    public int Id { get; set; }    

    public int  Value { get; set; }

    public string Matricola { get; set; }

     // add property IsVisible
    private bool _isVisible;
    public bool IsVisible
    {
        set { SetProperty(ref _isVisible, value); }
        get { return _isVisible; }
    }

    bool SetProperty<T>(ref T storage, T value, [CallerMemberName] string propertyName = null)
    {
        if (Object.Equals(storage, value))
            return false;
        storage = value;
        OnPropertyChanged(propertyName);
        return true;
    }
    protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
    public event PropertyChangedEventHandler PropertyChanged;
}

2.create viewmodel (TestViewModel.cs)

public class TestViewModel:BaseViewModel 
{
    //add other code in this ViewModel

    public ObservableCollection<Item> Items { get; private set; }

    public TestViewModel() {

        Items = new ObservableCollection<Item>();   

        Items.Add(new Item { Id = 01, Value = 10, Matricola = "test1"});
        Items.Add(new Item { Id = 02, Value = 13, Matricola = "test2" });
        Items.Add(new Item { Id = 03, Value = 16, Matricola = "test3" });

    }

3.Usage example:

TestPage.xaml

<?xml version="1.0" encoding="utf-8" ?> 
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="MauiContentViewApp.TestPage"
             xmlns:MauiContentViewApp="clr-namespace:MauiContentViewApp;assembly=MauiContentViewApp"
             Title="TestPage">
    <VerticalStackLayout>
        <CollectionView ItemsSource="{Binding Items}">
            <CollectionView.ItemTemplate>
                <DataTemplate>
                    <Grid Padding="10">
                        <Grid.RowDefinitions>
                            <RowDefinition Height="Auto" />
                        </Grid.RowDefinitions>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="*" />
                            <ColumnDefinition Width="*" />
                        </Grid.ColumnDefinitions>

                        <Entry Grid.Column="0" 
                               BackgroundColor="Yellow"
                               Text="{Binding Value}" 
                               
                               Completed="Entry_Completed"  
                               VerticalOptions="Center" 
                               FontAttributes="Bold" />
                        <Label Grid.Row="1"
                               Grid.Column="1" 
                               Text="{Binding Matricola}"
                               
                               IsVisible="{Binding IsVisible}"
                               FontAttributes="Italic" 
                               VerticalOptions="Center" />
                    </Grid>
                </DataTemplate>
            </CollectionView.ItemTemplate>
        </CollectionView>
    </VerticalStackLayout>
</ContentPage>

TestPage.xaml.cs

public partial class TestPage : ContentPage 
{
      public TestPage()
      {
            InitializeComponent();

            BindingContext = new TestViewModel();
      }

    private void Entry_Completed(object sender, EventArgs e)
    {// here we can get the edited object and change the value of property `IsVisible` of this item ,then the `IsVisible` of `Matri` Label will be updated.
            Item item = (Item)((Entry)sender).BindingContext;

            if (item!=null && !item.IsVisible) {
            item.IsVisible= true;
        }
    }
}