Note - this is one of my earliest articles and I cannot guarantee that the sample is working and the presentation is clear. I plan to write another article that will incorporate the samples from my earliest articles making them work. Thanks for your understanding.
TreeView control does not give developers an ability to multi-select the nodes of the tree. This article shows a very simple example that simulates multi-select capability for a WPF
TreeView control. I say "simulate" because it discards the WPF select mechanism and replaces it with its own.
Ideally another user control called, say
MultiSelectTreeView, should be created and packed in a separate DLL, but since I do not have much time to spend on it, I simply showed how to do it by modifying the code in the main
To multi-select, you should use the left ctrl key on your keyboard together with the mouse. The shift key and ctrl-A multi-select functions were not added (again for the lack of time), but can be added in exactly the same manner.
Simulating the Multi-Selection
As stated above, we disable the WPF selection and, instead use our own selection mechanism, according to which, all
TreeViewItem elements that have been selected are stored in
selectedItems set. The set is simulated by a
The selected items change their
Foreground properties to
LeftCtrl key is not pressed, then, before selecting an item, we clean all the previous selections. If
LeftCtrl key is pressed, the previous selections are not cleaned.
Using the Code
The top level code is located in
MyTreeView_SelectedItemChanged function and called when
SelectedItemChanged event is fired on the
First, prevent WPF selection:
treeViewItem.IsSelected = false;
LeftCtrl is not pressed, clear the previous selections:
List<treeviewitem> selectedTreeViewItemList = new List<treeviewitem>();
foreach (TreeViewItem treeViewItem1 in selectedItems.Keys)
foreach (TreeViewItem treeViewItem1 in selectedTreeViewItemList)
Then, flip flop the selection state of the item: if selected, make it unselected and vice versa:
We check whether
LeftCtrl key is pressed or not by implementing the following property:
- 23rd March, 2008: Initial post