Turning a TreeViewItem into a ToggleButton We will examine the TreeView’s ItemContainerStyle in the next section. Similarly, clicking on the box in the CheckBox will not select that item, but clicking on the neighboring display text will. Clicking on the box element in the CheckBox will cause its check state to change, but clicking on the neighboring display text will not. This helps us satisfy Requirements 6 and 7. By using a separate ContentPresenter, rather than setting the CheckBox’s Content property, we can avoid that default behavior. By default, clicking anywhere on a CheckBox causes it to toggle its check state. Instead, there is a ContentPresenter directly next to it, whose Content is bound to the Name property of a FooViewModel object. The CheckBox’s IsChecked property is bound to the IsChecked property of a FooViewModel object, but notice that its Content property is not set to anything. We will address that issue later in this article, when we examine how to attach the behavior of a ToggleButton to a TreeViewItem. You might be wondering how we will be able to satisfy Requirement 5 if the CheckBox never has input focus. This prevents the CheckBox from ever receiving input focus, which assists in meeting Requirement 4. The template includes a CheckBox whose Focusable property is set to false. There are several points of interest in that template. The TreeView declaration is actually quite simple, as seen below: Now it is time to see how the TreeView is able to display checkboxes and bind to the ViewModel. If you have different rules regarding how and when items should update their check state, simply adjust the logic in those methods to suit your needs. This strategy is specific to the functional requirements I imposed upon myself. (c => c.SetIsChecked(_isChecked, true, false)) įor ( int i = 0 i < ++i)īool? current = If (updateChildren & _isChecked.HasValue) Void SetIsChecked( bool? value, bool updateChildren, bool updateParent) It is very easy to declare a CheckBox control in a TreeView’s ItemTemplate and suddenly every item in the tree contains a CheckBox. Since element composition and rich data binding are two core aspects of WPF, the WPF TreeView does not offer intrinsic support for displaying checkboxes. In some UI platforms, such as WinForms, the standard TreeView control offers built-in support for displaying checkboxes in its items. It is very common to have a TreeView whose items are checkboxes, such as when presenting the user with a hierarchical set of options to select. This article assumes that the reader is already familiar with data binding and templates, binding a TreeView to a ViewModel, and attached properties. This article also shows how to use the attached behavior concept to turn a TreeViewItem into a virtual ToggleButton, which helps make the TreeView’s keyboard interaction simple and intuitive. When a ViewModel object’s check state changes, it applies simple rules to the check state of its parent and child items. Each item is bound to a ViewModel object. This article reviews a WPF TreeView whose items contain checkboxes.
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