/// <summary>
/// Based on the solution proposed here:
/// Source: http://stackoverflow.com/questions/20244916/wpf-treeview-selection-change
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private static void uiElement_PreviewMouseDown(object sender, MouseButtonEventArgs e)
{
// first did the user click on a tree node?
var source = e.OriginalSource as DependencyObject;
while (source != null && !(source is TreeViewItem))
{
source = VisualTreeHelper.GetParent(source);
}
var itemSource = source as TreeViewItem;
if (itemSource == null)
{
return;
}
var treeView = sender as TreeView;
if (treeView == null)
{
return;
}
bool undoSelection = TreeViewSelectionChangedBehavior.GetUndoSelection(treeView);
if (undoSelection == false)
{
return;
}
// Cancel the attempt to select an item.
var result = MessageBox.Show("The current document has unsaved data. Do you want to continue without saving data?", "Are you really sure?",
MessageBoxButton.YesNo, MessageBoxImage.Question, MessageBoxResult.No);
if (result == MessageBoxResult.No)
{
// Cancel the attempt to select a differnet item.
e.Handled = true;
}
else
{
// Lets disable this for a moment, otherwise, we'll get into an event "recursion"
treeView.PreviewMouseDown -= uiElement_PreviewMouseDown;
// Select the new item - make sure a SelectedItemChanged event is fired in any case
// Even if this means that we have to deselect/select the one and the same item
if (itemSource.IsSelected == true)
{
itemSource.IsSelected = false;
}
itemSource.IsSelected = true;
// Lets enable this to get back to business for next selection
treeView.PreviewMouseDown += uiElement_PreviewMouseDown;
}
}
/// <summary>
/// This method is called when the selection changed event occurs. The sender should be the control
/// on which this behaviour is attached - so we convert the sender into a <seealso cref="UIElement"/>
/// and receive the Command through the <seealso cref="GetChangedCommand"/> getter listed above.
///
/// The <paramref name="e"/> parameter contains the standard EventArgs data,
/// which is unpacked and reales upon the bound command.
///
/// This implementation supports binding of delegate commands and routed commands.
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private static void Selection_Changed(object sender, RoutedPropertyChangedEventArgs <object> e)
{
var uiElement = sender as TreeView;
// Sanity check just in case this was somehow send by something else
if (uiElement == null)
{
return;
}
ICommand changedCommand = TreeViewSelectionChangedBehavior.GetChangedCommand(uiElement);
// There may not be a command bound to this after all
if (changedCommand == null)
{
return;
}
////if ((e.NewValue == null && e.NewValue == null))
//// return;
////else
////{
//// // Actual value did not really change
//// if ((e.NewValue != null && e.NewValue != null))
//// {
//// if ((e.NewValue == e.NewValue))
//// return;
//// }
////}
// Check whether this attached behaviour is bound to a RoutedCommand
if (changedCommand is RoutedCommand)
{
// Execute the routed command
(changedCommand as RoutedCommand).Execute(e.NewValue, uiElement);
}
else
{
// Execute the Command as bound delegate
changedCommand.Execute(e.NewValue);
}
}