Question

I have a problem with listView initializations. The .xaml part of the listView is as below,

<ListView x:Name="categoryListView" HorizontalAlignment="Left" Width="129" Height="180" 
              ItemsSource="{Binding Path=RecordModel.CategoryList}" 
              DisplayMemberPath="RecordModel.CategoryList" 
              SelectedValue="{Binding Path=RecordModel.RecordTitle}"
              VerticalAlignment="Top">

I have a list of String paths in RecordModel.CategoryList but I need to change the list at window initialization. Part of the view-model is below. Where can I add the code to change the list so the listView gets the changed list items at start?

public class MainWindowViewModel : ViewModelBase
{
...
private RecordModel _recordModel;
private ICommand _addCategoryCommand;
...

public MainWindowViewModel()
{
 _recordModel = new RecordModel();
}
public RecordModel RecordModel
{
  get { return _recordModel; }
  set { _recordModel = value; }
}
...
public ICommand AddCategoryCommand
{
 get
  {
   if (_addCategoryCommand == null)
       _addCategoryCommand = new AddCat ();
     return _addCategoryCommand;
  }
}

public class AddCat : ICommand
{
  public bool CanExecute(object parameter) { return true; }
  public event EventHandler CanExecuteChanged;
  public void Execute(object parameter)
  {
    MainWindowViewModel mainWindowViewModel = (MainWindowViewModel)parameter;
    ...
    //Do things with mainWindowViewModel and the variables it has
  }
...

Answer 1

This is the reason that ViewModels exist: so that they can transparently convert values from the Model to values more appropriate for binding.

You should expose a CategoryList property on the MainWindowViewModel and bind directly on that. You can then populate it by processing the values of RecordModel.CategoryList in the RecordModel property setter:

public class MainWindowViewModel : ViewModelBase
{
    private RecordModel _recordModel;

    public MainWindowViewModel()
    {
        RecordModel = new RecordModel(); // set the property not the field
    }

    public RecordModel RecordModel
    {
        get { return _recordModel; }
        set {
            _recordModel = value;
            // populate CategoryList here from value.CategoryList
        }
    }

    public UnknownType CategoryList { get; }
}