WinForm's ViewModelViewHost DefaultContent behavior is inconsistent with WPF.

[newbienewbie]

The WinForm applies the DefaultContent only when ViewModel is null and skip the the assignment of Content <- view when view becomes null:

if (ViewModel is null)       // ********************* the DefaultContent is applied only if ViewModel is NULL******************
{
    if (DefaultContent is not null)
    {
        Content = DefaultContent;
    }

    return;
}

if (CacheViews)
{
    // ...
}

 var viewLocator = ViewLocator ?? ReactiveUI.ViewLocator.Current;
 var view = viewLocator.ResolveView(x.ViewModel, x.Contract);
 if (view is not null)     // ********************* change the content only if view is not null ************************
 {
     view.ViewModel = x.ViewModel;
     Content = view;
 } 

While the WPF will set the Content = DefaultCotent in both cases :

    if (viewModel is null)
    {
        Content = DefaultContent;
        return;
    }
  ...

  if (viewInstance is null)
  {
      Content = DefaultContent;
      this.Log().Warn($"The {nameof(ViewModelViewHost)} could not find a valid view for the view model of type {viewModel.GetType()} and value {viewModel}.");
      return;
  }

In a WinForm App, if I dynamically change the ViewContractObservable to a contract that is not registered before (e.g. "Contract_That_Doesnot_Exist"), the above assignment Content <- view; within if(view is not null) { ... } won't be executed. As a result, the Content view remains the same.

However, in WPF, if a viewInstance becomes null, the Content will be set as DefaultContent.