Xamarin Form Stacklayout not resetting/Cached

We have a class that is consist of property say 'ItemJson' as JSON text, which is later convert to List<Class2> in read only property called 'Items'.. now we use that Items to bind a Stacklayout in UI. On button action we save the ItemJson to database through API and move user to thanks screen.
When user came back he is suppose to see blank screen and for that we have Viewmodel set to reinitialize our object using new keyword. But it doesn't clear the Stacklayout or the Items variable although ItemJson is blank out. This results in old Items are still visible to user.

So my class is (Example)

Myclass { 
 public string ItemJson {get; set;} 
 public List<Class2> Items { get { return JsonConvert.DeserializeObject<List<Class2>>(ItemJson); } }
}

And my UI use Items as

<Stacklayout Bindable="{Binding Obj.Items}" ... >
...DataTemplate etc..</Stacklayout>

My ViewModel has function called onAppearing of UI, that did

Obj = new MyClass();

But it doesn't clear the Items property.

EDIT:
I forgot to mention, We navigate through Shell.Current.GoToAsync() and I even try to use Shell.Current.Navigation.PushAsync() in hope that it don't reuse last UI screen and hence come blank. But it didn't work. We cannot recreate full screen through variable as in our process we have to switch to various screen in between and come back. so If recreate or rePush new object it effect the flow of application. So we need just to clear in when we press save button. And on Save button I try to reinitialize this object but it is getting cached by some internal programming.

Since you didn't share sufficient information (yet) about your code and the exact problem with it, I'll try to give a more generic answer based on how I understood your problem.

Make properties observable

Your class needs to implement the INotifyPropertyChanged interface in order to notify the UI about changes to the Items when the ItemJson changes:

public class Myclass : INotifyPropertyChanged { 
    public event PropertyChangedEventHandler PropertyChanged;  

    private void OnPropertyChanged([CallerMemberName] string propertyName = "")  
    {  
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }   

    private string _itemJson;
    public string ItemJson
    {
        get => _itemJson;
        set
        {
            if(_itemJson == value) return;
            _itemJson = value;
            OnPropertyChanged();
            OnPropertyChanged(nameof(Items));
        }
    }

    public List<Class2> Items { get { return JsonConvert.DeserializeObject<List<Class2>>(ItemJson); } }
}

If the Items object is supposed to be empty, you need to set the ItemJson to an empty JSON array, e.g.:

Obj.ItemJson = "[]";

This will clear the list, because OnPropertyChanged(nameof(Items)); is called by the property setter, which then notifies the UI to update the binding to Items.

Some notes and suggestions for improvement

This is not an ideal implementation, but that's because the setup of your Page and ViewModel doesn't seem to be well-designed (again, basing this on little actual information).

You shouldn't deserialize the JSON inside of a property getter - what if an exception is thrown by the parser? It's also not a good design to have a dependency on a JSON structure, because you shouldn't need to have an empty array or list in order to update the Items property to become empty.

Rather, you should directly set the Items property, which should also be observable:

private List<Class2> _items;
public List<Class2> Items
{
    get => _items;
    set
    {
        if(_items == value) return;
        _items = value;
        OnPropertyChanged();
    }
}

Then you can set the list directly after deserializing the JSON, e.g.:

public void UpdateData(string json)
{
    try
    {
        List<Class2> newData = JsonConvert.DeserializeObject<List<Class2>>(json);
        Items = newData;
    }
    catch(Exception ex)
    {
        Console.WriteLine(ex);
        Items = new List<Class2>();
    }
}

public void ClearData()
{
    Items = new List<Class2>();
}