Setting the TreeView "HasItems" Property when using a ObservableCollection

11-06-2009 4:20 PM |

I assumed that building a heirarchical observablecollection using a class derived from ObservableCollection (i.e. public class productcategory : ObservableCollection<productcategory>) would be traversable by a treeview if the binding in the HeirarchicalDataTemplate is set to the Items property (i.e. ItemsSource="{Binding Items}".

It appears that the TreeViewItem class has a readonly property "HasItems" property. Is the traversal activated by that property? See the bottom of the screenshot below. It is set to false. As you can see in the second screenshot, the item is aware of the observablecollection which was added and has three items, each of which is another observablecollection. If the treeview's itemssource is a observablecollection, how is that property set? Why don't I see a heirarchy of TreeViewIItems?

Maybe I am just grasping for why my treeview is not expandable...

Re: Setting the TreeView "HasItems" Property when using a ObservableCollection

11-06-2009 6:52 PM |

I'm just wondering if some of these properties only get set after the control loads into its parent, not initialized but loaded.

I think you're looking were you initialize.  Try looking later, in some other event.

Re: Setting the TreeView "HasItems" Property when using a ObservableCollection

11-07-2009 5:39 AM |

Thanks for replying. 

As the control exists in XAML and I can see it in the SL app with the top level items, I would think it was loaded. I would have thought it would get set after the itemssources was set and the observablecollection was attached.

Re: Setting the TreeView "HasItems" Property when using a ObservableCollection

11-07-2009 1:34 PM |

I guess I should have said "after the event that you are in".  I think it may need to finish this event, go back to the ui thread and, maybe, get an "update layout" event before it can finish up whatever housekeeping it needs to do.  Then, perhaps, these properties will be set.

But this is all speculation on my part.

Re: Setting the TreeView "HasItems" Property when using a ObservableCollection

11-08-2009 11:56 AM |

Actually I am calling the update layout from the code behind after adding to the collection.

Re: Setting the TreeView "HasItems" Property when using a ObservableCollection

11-15-2009 4:21 PM |

Min,

Thanks for replying. 

In this case, the ItemsSource is a ObservableCollection<xxx.productcategory> where xxx.productcategory is derived from ObservableCollection<xxx.productcategory> ... i.e.

public System.Collections.ObjectModel.ObservableCollection<productcategory> ProductCategories = new System.Collections.ObjectModel.ObservableCollection<productcategory>();

public class productcategory : ObservableCollection<productcategory>
{
    private MoneyPinchers.Web.Category _category;
    private string _name;
    private Int64 _UID;
}

I add sub-categories to the collection by selecting a category in the collection and using the inherited xxx.Add method, i.e.         CurrentCategory.Add(newcategory), so I from what I understand the overall collection should be traversable as they appear as members of the Items attribute of the parent category.

Marc