Issue with Combo box Item Template - wpf

Question

Please find the below code.
public enum SortByType
{
[Display(Name = "Y Value")]
Y_Value,
[Display(Name = "X Value")]
X_Value,
[Display(Name = "Z Value")]
Z_Value,
}
public class ViewModel : INotifyPropertyChanged
{
ObservableCollection<SortByType> sortList;
SortByType selectedType;
public ViewModel()
{
SortList = new ObservableCollection<SortByType>(Enum.GetValues(typeof(SortByType)).OfType<SortByType>().ToList());
}
public ObservableCollection<SortByType> SortList
{
get
{
return sortList;
}
set
{
sortList = value;
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(SortList)));
}
}
public SortByType SelectedType
{
get
{
return selectedType;
}
set
{
selectedType = value;
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(SelectedType)));
}
}
public event PropertyChangedEventHandler PropertyChanged;
}
public partial class MainWindow : Window
{
public MainWindow()
{
DataContext = new ViewModel();
(DataContext as ViewModel).SelectedType = SortByType.Y_Value;
InitializeComponent();
}
private void Button_Click(object sender, RoutedEventArgs e)
{
(DataContext as ViewModel).SortList.Clear();
(DataContext as ViewModel).SortList = new ObservableCollection<SortByType>(Enum.GetValues(typeof(SortByType)).OfType<SortByType>().ToList());
}
}
<Grid>
<StackPanel VerticalAlignment="Center">
<ComboBox ItemsSource="{Binding SortList}"
SelectedItem="{Binding SelectedType}">
<ComboBox.ItemTemplate>
<DataTemplate>
<Label Content="{Binding}"/>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
<Button Height="25" Width="150" Content="Details" Click="Button_Click"/>
</StackPanel>
</Grid>
Just, Clear the collection and re-initialize the combo box item source on button click event. On this time I have noticed that the Data error shown on the combo box. Can anyone explain what is the exact problem whether it may be a memory issue or some thing i have missed while implement the Item Template

Answer 1

The value of SelectedType must be present in the source collection. It's not when you assign the source property to a new list of new values, unless you set explicitly set it to any of these new values:
private void Button_Click(object sender, RoutedEventArgs e)
{
var viewModel = DataContext as Win32ViewModel;
viewModel.SortList = new ObservableCollection<SortByType>(Enum.GetValues(typeof(SortByType)).OfType<SortByType>().ToList());
viewModel.SelectedType = viewModel.SortList.FirstOrDefault(x => x == viewModel.SelectedType);
}