using MiniMvvm; namespace VirtualizationDemo.ViewModels; public class ExpanderItemViewModel : ViewModelBase { private string? _header; private bool _isExpanded; public string? Header { get => _header; set => RaiseAndSetIfChanged(ref _header, value); } public bool IsExpanded { get => _isExpanded; set => RaiseAndSetIfChanged(ref _isExpanded, value); } }