I have successfully used a few custom commands using MVVM-Light, but I want my application to respond to the standard ApplicationCommands, not just at a Window level, but at a detailed item level as well.
I have a TreeView
that I want to be able to copy and paste nodes in. Each TreeViewItem has its own ViewModel, and they are displayed via HierarchicalDataTemplates
in XAML as there are several different types. I have implemented methods to copy, paste, as well as CanCopy and CanPaste on my ViewModel classes. If appropriate, I could implement MVVM-Light RelayCommands pointing to these easily enough, but that doesn't seem right.
I would like to access the commands using a menu, Ctrl+C and Ctrl+V, or eventually a context menu. I also don't want to break copy/paste functionality for other elements in my UI, such as TextBoxes. It seems appropriate to use the built-in ApplicationCommands for this purpose. However, I am only seeing examples of these being handled in a UserControl code-behind. I don't have (or otherwise need) a UserControl, nor is that really following MVVM.
Is there a way I can bind ApplicationCommand.Copy
and ApplicationCommand.Paste
commands to my ViewModels, i.e., in the data templates?
I have resolved this using Behaviors attached to the TreeView. The TreeViewItems or Templates to not seem to get the commands routed to them. Fortunately, the TreeView also has a SelectedItem property that can be used to get the ViewModel!
(Behaviors are conceptually similar to the solution in the link in @Natxo's answer, but it doesn't resolve everything.)
The Behavior class:
public class TreeViewClipboardBehavior : Behavior<TreeView>
{
protected override void OnAttached()
{
base.OnAttached();
CommandBinding CopyCommandBinding = new CommandBinding(
ApplicationCommands.Copy,
CopyCommandExecuted,
CopyCommandCanExecute);
AssociatedObject.CommandBindings.Add(CopyCommandBinding);
CommandBinding CutCommandBinding = new CommandBinding(
ApplicationCommands.Cut,
CutCommandExecuted,
CutCommandCanExecute);
AssociatedObject.CommandBindings.Add(CutCommandBinding);
CommandBinding PasteCommandBinding = new CommandBinding(
ApplicationCommands.Paste,
PasteCommandExecuted,
PasteCommandCanExecute);
AssociatedObject.CommandBindings.Add(PasteCommandBinding);
}
private void CopyCommandExecuted(object target, ExecutedRoutedEventArgs e)
{
NestingItemTreeViewModelBase item = AssociatedObject.SelectedItem as NestingItemTreeViewModelBase;
if (item != null && item.CanCopyToClipboard)
{
item.CopyToClipboard();
e.Handled = true;
}
}
private void CopyCommandCanExecute(object target, CanExecuteRoutedEventArgs e)
{
NestingItemTreeViewModelBase item = AssociatedObject.SelectedItem as NestingItemTreeViewModelBase;
if (item != null)
{
e.CanExecute = item.CanCopyToClipboard;
e.Handled = true;
}
}
private void CutCommandExecuted(object target, ExecutedRoutedEventArgs e)
{
NestingItemTreeViewModelBase item = AssociatedObject.SelectedItem as NestingItemTreeViewModelBase;
if (item != null && item.CanCutToClipboard)
{
item.CutToClipboard();
e.Handled = true;
}
}
private void CutCommandCanExecute(object target, CanExecuteRoutedEventArgs e)
{
NestingItemTreeViewModelBase item = AssociatedObject.SelectedItem as NestingItemTreeViewModelBase;
if (item != null)
{
e.CanExecute = item.CanCutToClipboard;
e.Handled = true;
}
}
private void PasteCommandExecuted(object target, ExecutedRoutedEventArgs e)
{
NestingItemTreeViewModelBase item = AssociatedObject.SelectedItem as NestingItemTreeViewModelBase;
if (item != null && item.CanPasteFromClipboard)
{
item.PasteFromClipboard();
e.Handled = true;
}
}
private void PasteCommandCanExecute(object target, CanExecuteRoutedEventArgs e)
{
NestingItemTreeViewModelBase item = AssociatedObject.SelectedItem as NestingItemTreeViewModelBase;
if (item != null)
{
e.CanExecute = item.CanPasteFromClipboard;
e.Handled = true;
}
}
}
The XAML
<TreeView Grid.Row="2" ItemsSource="{Binding SystemTreeRoot}">
<i:Interaction.Behaviors>
<local:TreeViewClipboardBehavior/>
</i:Interaction.Behaviors>
<TreeView.Resources>
<HierarchicalDataTemplate DataType="{x:Type local:MyViewModel}" ItemsSource="{Binding Children}">
<!-- Template content -->
</HierarchicalDataTemplate>
</TreeView>