wpf mvvm treeview get selected item

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To get I am trying the following code but it the IsSelected property is not getting updated when I select an item in the treeview. Please guide me how to resolve this. Actually my requirement is to do some functionality on selecting an item in the treeview.

XML

<TreeView ItemsSource="{Binding TreeData}">
    <TreeView.ItemContainerStyle>
        <Style TargetType="{x:Type TreeViewItem}">
            <Setter Property="IsSelected" Value="{Binding IsSelected}" />
        </Style>
    </TreeView.ItemContainerStyle>
</TreeView>

C#

public class TViewModel : INotifyPropertyChanged
{
    private static object _selectedItem = null;
    // This is public get-only here but you could implement a public setter which also selects the item.
    // Also this should be moved to an instance property on a VM for the whole tree, otherwise there will be conflicts for more than one tree.
    public static object SelectedItem
    {
        get { return _selectedItem; }
        private set
        {
            if (_selectedItem != value)
            {
                _selectedItem = value;
                OnSelectedItemChanged();
            }
        }
    }

    static virtual void OnSelectedItemChanged()
    {
        // Raise event / do other things
    }

    private bool _isSelected;
    public bool IsSelected
    {
        get { return _isSelected; }
        set
        {
            if (_isSelected != value)
            {
                _isSelected = value;
                OnPropertyChanged("IsSelected");
                if (_isSelected)
                {
                    SelectedItem = this;
                }
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged(string propertyName)
    {
        if (this.PropertyChanged != null)
        {
            this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

[edit]code block fixed[/edit]

Posted 15-Dec-12 6:43am

Nekka

Updated 15-Dec-12 7:00am

Nelek

v2

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theHollow · Answer 1 · 2012-12-15T09:31:00

HTML

Hello
I would approach this by creating a control that inherits TreeView, and has the SelectedItem property with a dependency property so it can be used in XAML code and bindings. Let's call the control MyTreeView.

NOTE: By doing this, I don't kow if the property can be SET, but it can certainly be used to get the selected item.

Here's some example code for the control:

C#

public class MyTreeView : TreeView, INotifyPropertyChanged
{
    public static readonly DependencyProperty SelectedItemsProperty = DependencyProperty.Register("SelectedItem", typeof(Object), typeof(MyTreeView), new PropertyMetadata(null));
    public new Object SelectedItem
    {
        get { return (Object)GetValue(SelectedItemProperty); }
        set
        {
            SetValue(SelectedItemsProperty, value);
            NotifyPropertyChanged("SelectedItem");
        }
    }

    public MyTreeView()
        : base()
    {
        base.SelectedItemChanged += new RoutedPropertyChangedEventHandler<Object>(MyTreeView_SelectedItemChanged);
    }

    private void MyTreeView_SelectedItemChanged(Object sender, RoutedPropertyChangedEventArgs<Object> e)
    {
        this.SelectedItem = base.SelectedItem;
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged(String aPropertyName)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(aPropertyName));
    }
}

You can now use your control as an ordinary TreeView control, with your alterations.

HTML

<grid>
    <local:mytreeview itemssource="{Binding Path=Items, Mode=OneWay}" xmlns:local="#unknown">
                      SelectedItem="{Binding Path=SelectedItem, Mode=TwoWay}"
                      Margin="0,0,0,20" />
    <textblock text="{Binding Path=SelectedItem, Mode=OneWay}">
               VerticalAlignment="Bottom" />
</textblock></local:mytreeview></grid>

Hope it helps!

Nekka · Answer 2 · 2012-12-18T00:26:00

Hi, Thanks for your reply.

I tried this and I am able to view the Selected item in the dependency property class. But I wan to access this selected item in my view's view model class. Please let me know how to do this.

I tried to implement this by binding it to a property in the viewmodel but itsis not working. Please let me know how to do this.

Thanks in Advance.

theHollow · Answer 3 · 2012-12-25T11:41:00

Hi The model class should be the view's DataContext.

In the view class, you can set this either in the constructor by code"

C#

this.DataContext = new ViewClass();

Or in the XAML, in the starting tag:

XML

<viewmodel mode="hold" />                        DataContext="{local:ViewClass}"  />

Now, you can bind form the XAML.
Hope it helped.

wpf mvvm treeview get selected item

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