I’ve posted an update for my WPF TreeView which contains a bugfix and two new features:

• The root item collection is now monitored for changes, and the tree updates itself automatically. This behaviour, however, can be controlled through the ObserveRootItems dependency property.
• Built-in filtering support through a strongly typed predicate. I’m not completely happy with my implementation though – as a matter of fact, I’ve already started to rewrite it completely – you can expect the next version within the next 10 days. The filtering API however, will remain intact.

In case you did override some of the tree’s virtual methods, your project might not compile out of the box because some of these methods now receive additional parameters. However, as nothing has been removed, adjusting your code should be a matter of seconds.

I’ve added the download link to the original post:
http://www.hardcodet.net/2008/01/wpf-treeview

Happy coding 🙂

I abandoned the LGPL in favor of the Code Project Open License (CPOL) this morning (starting with the TreeView control), and I was pretty surprised that Googling for the license didn’t show up the license’s home page in the upper ranks.

As a result, I decided to write my first Wikipedia article in order to make this – IMO very nice license – at bit more accessible. The article itself is no big deal, but I must say, writing on Wikipedia is very convenient – I think I might do that again 🙂

Robby Ingebretsen published the source code of his incredibly useful (and beautiful!) Kaxaml on CodePlex. I often prefer Kaxaml over Visual Studio because it combines a bunch of really smart features with a very nice UI that just makes it a pleasure to work with. I’m definitely looking forward to have a peek at its internals 🙂

CodePlex project site: http://www.codeplex.com/Kaxaml
Official Kaxaml download site: http://www.kaxaml.com

A tutorial is now available on Code Project, so check the article for a detailed overview. And please leave your rating if you like the control 🙂
http://www.codeproject.com/KB/WPF/versatile_treeview.aspx

Update: The latest version is currently only available through the download link below. I’ll update the CodeProject article once the current filtering mechanism has been rewritten:

Download: wpf-treeview.zip (Current version: 1.0.7, updated 2008.04.06)

This is a little something I’ve been working on for a while: A replacement (or better: enhancement) of WPF’s built-in TreeView control.

I became aware of the default control’s limitations during my last project – I naturally started with hierarchical data templates, but was soon confronted with quite a few issues: I missed a simple API to control the tree, and styling of the tree’s nodes proved hard as well. Furthermore, WPF’s TreeView tends to fire all sorts of SelectedItemChanged events if it’s being refreshed or rebound, which caused side-effects with TwoWay data binding.

However, instead of posting a rant that probably nobody would ever read (let alone care about), I worked on an alternative. Here’s the tree’s main features at a glance:

• Simple declaration:

  <local:ProductTree x:Name="MyTree"
                     Items="{Binding Source={StaticResource Shop},
                            Path=Products}"
                     SelectedItem="{Binding ElementName=MyProductList,
                            Path=ActiveItem, Mode=TwoWay}"
                     NodeContextMenu="{StaticResource CategoryMenu}"
                     TreeNodeStyle="{StaticResource SimpleFolders}"
                     TreeStyle="{StaticResource SimpleTreeStyle}"
                     SelectedItemChanged="OnSelectedItemChanged"
  />

• Simple and type safe API:

  //bind flat list of business objects to tree
  List<Product> products = GetProducts();
  myTree.Items = products;
  
  //select a given item
  Product foo = GetBestSellingProduct();
  myTree.SelectedItem = foo; 
  
  //SelectedItem is of type Product - no casts required
  Product bar = myTree.SelectedItem;

• Lazy loading support – does not create tree nodes until the parent node is expanded. Also provides the option to automatically clear invisible tree nodes. This allows either virtualized trees in case getting data is expensive, or low memory trees that keep the number of tree nodes at a minimum.
• Simple sorting.
• Convenient context menu handling for tree nodes
• Optional root node which is not dependent on the tree’s bound items
• Simple styling on every level: Tree, TreeViewItem, or bound items (via DataTemplates).
• Tree layout can be cached, saved and reapplied.
• Access to tree nodes (TreeViewItem) through bound items.
• AutoCollapse feature / ExpandAll / CollapseAll methods

All this goodness comes at a price: The TreeViewBase class that provides this functionality, is abstract. This means you have to write a little code yourself. However, you’ll probably manage with 3 lines of code, as the base control just needs to know 3 things:

• How to generate an identifier for a given tree node
• How to access a bound item’s childs, if there are any
• How to access a bound item’s parent, if there is one

Here’s the complete implementation of the sample application’s tree control:

//a tree control that handles only ShopCategory objects
public class CategoryTree : TreeViewBase<ShopCategory>
{

  //the sample uses the category's name as the identifier
  public override string GetItemKey(ShopCategory item)
  {
    return item.CategoryName;
  }

  //returns subcategories that should be available through the tree
  public override ICollection<ShopCategory>
                             GetChildItems(ShopCategory parent)
  {
    return parent.SubCategories;
  }

  //get the parent category, or null if it's a root category
  public override ShopCategory GetParentItem(ShopCategory item)
  {
    return item.ParentCategory;
  }

I’m planning to write a CodeProject article for this one, but for now, it’s only available through my place without a tutorial. However: The library comes with a sample project that shows pretty much all features of the control. Project format is currently VS2008 only, but binaries which target .NET 3.0 are included. Enjoy!

With this WPF progress dialog, you can display a progress window and invoke a method on a background thread with just a few lines of code. Let’s say, you have a worker method called CountTo100, then all you need to get things running is this:

//create a dialog instance
ProgressDialog dlg = new ProgressDialog();
dlg.Owner = this;
dlg.DialogText = "hello world";

//we cannot access the user interface on the worker thread, but we
//can submit an arbitrary object to the RunWorkerThread method
int startValue = int.Parse(txtStartValue.Text);

//start processing and submit the start value
dlg.RunWorkerThread(startValue, CountTo100);

RunWorkerThread displays the dialog as a modal window, and invokes CountTo100 on a background thread. Styling of the dialog is completely up to you, but here’s a screenshot of the dialog running in the sample application:

The dialog uses a BackgroundWorker component and supports updating both progress bar and displayed text directly from the worker thread. Cancelling support, returning results from the worker thread and simplified exception handling are available as well. In order to get you started in no time, I’ve created a little sample application that shows a few scenarios, including parameter submission and the handling of exceptions on the worker thread. Enjoy! 🙂

Download Sample (VS2008 / VS2005 projects included): wpfprogressdialog.zip