![]() ![]() A Key, which you can use later to refer to it.When using XML data as the source, you create an XMLDataProvider in the markup. Here is the content of the XML data file: To keep things short and simple, I have only included two SalesPerson instances in the demo file. Here is a schematic of the overall structure of the data:Īs you can see from the diagram, each Salesperson can have several children named 'Period', each Period can have several children named ''Order' and each Order can have several children named 'Item'. This has the advantage that you can physically see the tree-like composition of the data. Hopefully, if you too have come unstuck using these kind of templates, this step by step approach might be helpful to you. So I thought I would work through a few samples over the space of a few blogs, building up the complexity as I go. Although I understood the overall theory that they walk the data tree and can create formatted, nested output, I always seemed to spend an inordinately long time trying to get things to work just as I want them (or sometimes, to be truthful, to work at all!) IronPython & WPF: Data binding with TreeView's sel.For some reason, I struggled with HierarchicalDataTemplates when I first tried to use them.Self.children_collection = ObservableCollection(initchildren)īy running this example we can see how the label of the selected element of the TreeView is reflected in the TextBlock defined above. Self.sselected = NodeModel( selected(self): With this XAML definition we can write the following IronPython code:Ĭlr.AddReference( "PresentationFramework")Ĭlr.AddReference( '')įrom import XamlReaderįrom import TreeViewįrom GalaSoft.MvvmLight import ViewModelBaseįrom import ObservableCollection Having defined this attached property and helper class we can now write the following example. Set NETFX4=c:\WINDOWS\Microsoft.NET\Framework\v9\Ĭsc /debug /r:%NETFX4% /r:%WPFPATH%\WindowsBase.dll /r:%WPFPATH%\PresentationCore.dll /r:%WPFPATH%\PresentationFramework.dll /target:library utils.cs T.SelectedItemChanged += SelectedItemChanged TreeViewSelectedBehavior.MySelectedProperty, The following helper class is used to subscribe the SelectedItemChanged event and change " MySelected". SelectedHelper: which is used to as an object that modifies the value of MySelected when the selected item changes(see below).MySelected: the output property that is used to set the selected element in the view model.((TreeViewSelectedHelper)e.NewValue).Register((TreeView)depObj) ![]() T.SetValue(SelectedHelperProperty, theValue) Public static void SetSelectedHelper(TreeView t, Return (TreeViewSelectedHelper)t.GetValue(SelectedHelperProperty) Public static TreeViewSelectedHelper GetSelectedHelper(TreeView t) New UIPropertyMetadata(null,OnSelectedHelperChanged) Public static readonly DependencyProperty SelectedHelperProperty = T.SetValue(MySelectedProperty, theValue) Public static void SetMySelected(TreeView t, object theValue) ![]() Public static object GetMySelected(TreeView t) Public static readonly DependencyProperty MySelectedProperty = Public static class TreeViewSelectedBehavior I couldn't find a way to wrote the definition of the attached property in IronPython because it needed to be instanciated by XamlReader. We're going to define an attached property which works as an "output only" property that could be used with data binding. One alternative is to use a technique similar to the one described in the "Forwarding the Result of WPF Validation in MVVM" post. There are several ways to deal with this problem. The problem is that the SelectedValue (and SelectedItem) property is read-only. SystemError: 'Provide value on '' threw an exception.' Line number '12' and line position '7'. Running this code results on the following error: At first it seemed to be an easy task so I wrote: In this post I'm going to show a small example of using data binding with the selected element of a WPF TreeView with an IronPython class.Ī couple of days ago I had the necessity of using data binding to keep track of the selected value of a WPF TreeView. ![]()
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