Catel和TreeView示例

Question

我找到了一个将Catel与TreeView here一起使用的示例，但遗憾的是这个示例是基于Catel版本3.3构建的，我试图在Catel 4.0版本上重复它，但不幸的是它没有用。

当我尝试将我的项目（基于Catel 4.0版）绑定到类TreeViewItemToDataContext中的属性时，缺少对UserControl中ViewModel的引用。

但该示例基于3.3版，一切正常。我想使用IViewModelManager手动获取链接，但遗憾的是在版本4中，版本3.3中没有生成viewModel，一切正常。

问我如何在Catel 4.0版上运行该示例？ 附： My test App

更新

public class TreeViewItemToDataContext : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        var uc = value as Catel.Windows.Controls.UserControl;

        if (uc != null)
        {
            uc.ViewModelChanged += this.OnViewModelChanged;
            return uc.DataContext;
        }

        return Binding.DoNothing;
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }

    private void OnViewModelChanged(object sender, EventArgs eventArgs)
    {
        var uc = sender as Catel.Windows.Controls.UserControl;
        if (uc != null)
        {
            var visualParent = uc.TemplatedParent as ContentPresenter;
            if (visualParent != null)
            {
                var treeViewItem = visualParent.TemplatedParent as TreeViewItem;
                if (treeViewItem != null)
                {
                    var IsSelectedBinding = new Binding("IsSelected");
                    IsSelectedBinding.Mode = BindingMode.TwoWay;
                    IsSelectedBinding.Source = uc.ViewModel;
                    treeViewItem.SetBinding(TreeViewItem.IsSelectedProperty, IsSelectedBinding);

                    var IsExpandedBinding = new Binding("IsExpanded");
                    IsExpandedBinding.Mode = BindingMode.TwoWay;
                    IsExpandedBinding.Source = uc.ViewModel;
                    treeViewItem.SetBinding(TreeViewItem.IsExpandedProperty, IsExpandedBinding);

                    uc.ViewModelChanged -= this.OnViewModelChanged;
                }
            }
        }
    }
}

ExpandCommand

 private void OnSetFocusAndExpandCommandExecute()
    {
        var model = this.ProviderGroups[0]; // open First Level
        var viewModelManager = this.GetServiceLocator().ResolveType<IViewModelManager>();
        var viewModels = viewModelManager.GetViewModelsOfModel(model);
        if (viewModels.Length > 0)
        {
            // NOTE: Somehow there are two viewmodels per model 
            var viewModel = viewModels[0] as TreeViewItemViewModel;
            if (viewModel != null)
            {
                //viewModel.IsSelected = true;
                viewModel.IsExpanded = true;
            }
        }

        var model1 = this.ProviderGroups[0].Categories.First();  // open Second Level
        var viewModels1 = viewModelManager.GetViewModelsOfModel(model1); // ViewModel Not created. 
        if (viewModels1.Length > 0)
        {
            // NOTE: Somehow there are two viewmodels per model 
            var viewModel1 = viewModels1[0] as TreeViewItemViewModel;
            if (viewModel1 != null)
            {
                viewModel1.IsSelected = true;
                viewModel1.IsExpanded = true;
            }
        }
    }

Answer 1

Catel中的视图模型现在加载时，实际上只需要它们（延迟加载）而不是急切加载。如果您覆盖用户控件上的 OnViewModelChanged ，您将看到它稍后被设置。

您可以订阅转换后的ViewModelChanged事件并等待第一个事件（不要忘记取消订阅）。