![]() 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.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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