HowTo implement commands for selection of treenodes in WPF treeview - wpf

Question

Again I'm a bit lost in WPF treeview.
I populated my treeview with some data and I'd like to fire a command, when clicking on a node and get its values in that command.
My treeview-xaml looks like this:
<TreeView DataContext="{Binding ProjectTree}" ItemsSource="{Binding ProjectNode}" DockPanel.Dock="Left" Margin="0 0 2 0" x:Name="ProjectTree" Grid.Column="0">
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}"/>
<Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}"/>
<Setter Property="FontWeight" Value="Normal"/>
<Style.Triggers>
<Trigger Property="IsSelected" Value="True">
<Setter Property="FontWeight" Value="Bold"/>
</Trigger>
</Style.Triggers>
</Style>
</TreeView.ItemContainerStyle>
<TreeView.ItemTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding Children}">
<StackPanel Orientation="Horizontal">
<Image Margin="3" Source="{Binding ItemType, Converter={x:Static misc:TreeItemImageConverter.Instance }}" Width="20" />
<TextBlock VerticalAlignment="Center" Text="{Binding Name}"/>
</StackPanel>
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
</TreeView>
How can I trigger a command on click on a treeviewitem here?
SOLUTION
After some experiments, It works for me that way:
xaml:
<TreeView DataContext="{Binding ProjectTree}" ItemsSource="{Binding ProjectNode}" DockPanel.Dock="Left"
x:Name="ProjectTree" Margin="0 0 2 0" Grid.Column="0">
<i:Interaction.Triggers>
<i:EventTrigger EventName="SelectedItemChanged">
<i:InvokeCommandAction Command="{Binding TreeNodeSelected}"
CommandParameter="{Binding ElementName=ProjectTree, Path=SelectedItem}"/>
</i:EventTrigger>
</i:Interaction.Triggers>
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}"/>
<Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}"/>
<Setter Property="FontWeight" Value="Normal"/>
<Style.Triggers>
<Trigger Property="IsSelected" Value="True">
<Setter Property="FontWeight" Value="Bold"/>
</Trigger>
</Style.Triggers>
</Style>
</TreeView.ItemContainerStyle>
<TreeView.ItemTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding Children}">
<StackPanel Orientation="Horizontal">
<Image Margin="3" Source="{Binding ItemType, Converter={x:Static misc:TreeItemImageConverter.Instance }}" Width="20" />
<TextBlock VerticalAlignment="Center" Text="{Binding Name}"/>
</StackPanel>
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
</TreeView>
In the Viewmodel of the treeview:
C#
public RelayCommand TreeNodeSelected { get; private set; }
readonly ReadOnlyCollection<PlcAddressViewModel> _rootNodes;
readonly PlcAddressViewModel _rootAddress;
#region Constructor
public ProjectTreeviewModel(PlcAddress rootAddress)
{
_rootAddress = new PlcAddressViewModel(rootAddress);
_rootNodes = new ReadOnlyCollection<PlcAddressViewModel>(
new PlcAddressViewModel[]
{
_rootAddress
});
TreeNodeSelected = new RelayCommand(ExecuteTreeNodeSelected, canExecuteMethod);
}
#endregion Constructor
#region Commands
private bool canExecuteMethod(object parameter)
{
return true;
}
private void ExecuteTreeNodeSelected(object parameter)
{
PlcAddressViewModel selectedNode = (PlcAddressViewModel)parameter;
Console.WriteLine("Found this node: " + selectedNode.Name);
return;
}
#endregion Commands
Thanks to #mm8 and #BionicCode

Answer 1

You could handle an event like for example SelectedItemChanged using an interaction trigger:
<TreeView DataContext="{Binding ProjectTree}"
ItemsSource="{Binding ProjectNode}"
x:Name="ProjectTree"
xmlns:i="http://schemas.microsoft.com/xaml/behaviors">
<i:Interaction.Triggers>
<i:EventTrigger EventName="SelectedItemChanged" >
<i:InvokeCommandAction Command="{Binding MouseEnterCommand}" />
</i:EventTrigger>
</i:Interaction.Triggers>
<TreeView.ItemContainerStyle>
...
</TreeView.ItemContainerStyle>
...
</TreeView>
Handling events in an MVVM WPF application
How to add System.Windows.Interactivity to project?
But why don't you just bind the SelectedItem property to a source property and handle your logic in the setter of this one? This would be MVVM way of doing this.
Edit: Since the SelectedItem property a TreeView is read-only, you'll have to use a behaviour to be able to bind to it. There is an example of how to do this here.