MVVM Treeview Click Node - wpf

Question

I am using an existed MVVM project and I did fine until now. I have a treeView code and I want
to release the node when it pressed. in other words, today if I click on any node, Its not selectable anymore (until you click another node). I want to be able to click thesame node as many times as I want. If I double click node , I have "IsExpended" property and it goes to this code section. I cant see where is the doubleclick bind, single click binding...
Here's the xaml
<UserControl x:Class="Envitech.Setup.Presentation.Views.TreeViewViews.StationTree" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:behaviour="clr-namespace:Envitech.Setup.Presentation.Extensions;assembly=Envitech.Setup.Presentation" xmlns:nodes="clr-namespace:Envitech.Setup.Presentation.ViewModels.TreeViewViewModels.Nodes" mc:Ignorable="d" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" d:DesignHeight="226" d:DesignWidth="227" xmlns:ml="clr-namespace:Envitech.Setup.Presentation.ml_resources">
<TreeView Margin="10 0 10 20" ItemsSource="{Binding Path=Root.Children}" VirtualizingStackPanel.IsVirtualizing="True" VirtualizingStackPanel.VirtualizationMode="Recycling">
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="IsSelected" Value="{Binding Path=IsSelected, Mode=TwoWay}"/>
<Setter Property="IsExpanded" Value="{Binding Path=IsExpanded, Mode=TwoWay}" />
</Style>
</TreeView.ItemContainerStyle>
<TreeView.Resources>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="Background" Value="Transparent" />
<Setter Property="HorizontalContentAlignment" Value="{Binding Path=HorizontalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}" />
<Setter Property="VerticalContentAlignment" Value="{Binding Path=VerticalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}" />
<Setter Property="Padding" Value="1,0,0,0" />
<Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}" />
<Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}" />
<Setter Property="behaviour:TreeViewItemBehavior.IsBroughtIntoViewWhenSelected" Value="True" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TreeViewItem}">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition MinWidth="19" Width="Auto" />
<ColumnDefinition Width="Auto" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition />
</Grid.RowDefinitions>
<ToggleButton x:Name="Expander" IsChecked="{Binding Path=IsExpanded, RelativeSource={RelativeSource TemplatedParent}}" ClickMode="Press" />
<Border Grid.Column="1" x:Name="Selection_Border" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Padding="{TemplateBinding Padding}">
<ContentPresenter HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" x:Name="PART_Header" ContentSource="Header" />
</Border>
<ItemsPresenter Grid.Column="1" Grid.ColumnSpan="2" Grid.Row="1" x:Name="ItemsHost" />
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsExpanded" Value="false">
<Setter Property="Visibility" Value="Collapsed" TargetName="ItemsHost" />
</Trigger>
<Trigger Property="HasItems" Value="false">
<Setter Property="Visibility" Value="Hidden" TargetName="Expander" />
</Trigger>
<Trigger Property="IsSelected" Value="true">
<Setter Property="Background" Value="{DynamicResource {x:Static SystemColors.HighlightBrushKey}}" TargetName="Selection_Border" />
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.HighlightTextBrushKey}}" />
</Trigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsSelected" Value="true" />
<Condition Property="IsSelectionActive" Value="false" />
</MultiTrigger.Conditions>
<Setter Property="Background" Value="{DynamicResource {x:Static SystemColors.HighlightBrushKey}}" TargetName="Selection_Border" />
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.HighlightTextBrushKey}}" />
</MultiTrigger>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<!-- Style for the ToggleButton control used to expand/collapse a TreeViewItem control -->
<Style TargetType="{x:Type ToggleButton}">
<Setter Property="Focusable" Value="False" />
<Setter Property="Width" Value="19" />
<Setter Property="Height" Value="13" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ToggleButton}">
<Border Width="19" Height="13" Background="#00FFFFFF" x:Name="Border">
<Border Width="9" Height="9" x:Name="Border1" SnapsToDevicePixels="True" BorderBrush="#FF9495A2" BorderThickness="1,1,1,1" CornerRadius="1,1,1,1">
<Border.Background>
<LinearGradientBrush StartPoint="0,0" EndPoint="1,1">
<GradientStop Color="#FFFFFFFF" Offset="0.4" />
<GradientStop Color="#FFC6CEDA" Offset="1" />
</LinearGradientBrush>
</Border.Background>
<Path Fill="#FF000000" Margin="1,1,1,1" x:Name="ExpandPath" Data="M0,2L0,3 2,3 2,5 3,5 3,3 5,3 5,2 3,2 3,0 2,0 2,2z" />
</Border>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsChecked" Value="True">
<Setter Property="Data" Value="M0,2L0,3 5,3 5,2z" TargetName="ExpandPath" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<DataTemplate DataType="{x:Type nodes:MonitorNode}">
<StackPanel Orientation="Horizontal" Margin="0 2 0 0">
<Image Source="{Binding ImageSource}" Width="16" Height="16" Margin="0 0 3 0" />
<TextBlock Text="{x:Static ml:MultiLang._157}" x:Name="ML_0048" />
<TextBlock Text="{Binding ID}" />
<TextBlock Text="{x:Static ml:MultiLang._158}" x:Name="ML_0050" />
<TextBlock Text="{Binding Name}" />
</StackPanel>
</DataTemplate>
<HierarchicalDataTemplate DataType="{x:Type nodes:StationNode}" ItemsSource="{Binding Children}">
<StackPanel Orientation="Horizontal" Margin="0 2 0 0">
<StackPanel.ContextMenu>
<ContextMenu HasDropShadow="True">
<MenuItem Header="{x:Static ml:MultiLang._160}" Command="{Binding CopyMonitorsCommand}" x:Name="ML_0055" />
<MenuItem Header="{x:Static ml:MultiLang._159}" Command="{Binding PasteMonitorsCommand}" x:Name="ML_0056" />
<MenuItem Header="{x:Static ml:MultiLang._162}" Command="{Binding CopyStationsCommand}" x:Name="ML_0057" />
<MenuItem Header="{x:Static ml:MultiLang._161}" Command="{Binding PasteStationsCommand}" x:Name="ML_0058" />
</ContextMenu>
</StackPanel.ContextMenu>
<Image Source="{Binding ImageSource}" Width="16" Height="16" Margin="0 0 3 0" />
<TextBlock Text="{x:Static ml:MultiLang._157}" x:Name="ML_0060" />
<TextBlock Text="{Binding ID}" />
<TextBlock Text="{x:Static ml:MultiLang._158}" x:Name="ML_0062" />
<TextBlock Text="{Binding Name}" />
</StackPanel>
</HierarchicalDataTemplate>
<HierarchicalDataTemplate DataType="{x:Type nodes:FilteringNode}" ItemsSource="{Binding Children}">
<StackPanel Orientation="Horizontal" Margin="0 2 0 0">
<Image Source="{Binding ImageSource}" Width="16" Height="16" Margin="0 0 3 0" />
<TextBlock Text="{Binding Name}" />
</StackPanel>
</HierarchicalDataTemplate>
</TreeView.Resources>
</TreeView>
</UserControl>
Thank you

Answer 1

When you double click a tree view item, it will be expanded. When it is expanded, your IsExpanded property will be changed due to your binding. Single clicking something that is NOT currently selected will change your IsSelected property. However, clicking it again (not double clicking) will NOT change the IsSelected property. Seems like what you want to do is to also add a 'Click' event handler. This way, each time it is clicked, you will be notified, not just when it is clicked for the first time when something else was selected.
To Accomplish this, add an for the 'MouseDoubleClick' event to your TreeViewItem style. If you want a single click, just do the same for the 'MouseDown' event:
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="IsSelected" Value="{Binding Path=IsSelected, Mode=TwoWay}"/>
<Setter Property="IsExpanded" Value="{Binding Path=IsExpanded, Mode=TwoWay}" />
<EventSetter Event="MouseDoubleClick" Handler="DoubleClickedItem"/>
</Style>
Once your XAML has the code above in it, right click your mouse on the word 'DoubleClickedItem' and select the 'NavigateToHandler' option and Visual Studio will generate a method stub for you in your code behind. You can then implement your double click behavior there.

Answer 2

This answer explains how to use the Interactivity extensions to remain fully MVVM.
WPF RightClick MouseBinding on release?
I've not been able to use the MouseLeftButtonDown event but MouseLeftButtonUp worked in my case (notification of a click on an already selected TreeViewItem).
I'm guessing that MouseLeftButtonDown is handled earlier in the event tree, so we never get to see it.