WPF Cannot see SelectedItem in TreeView

Question

WPF Cannot see SelectedItem in TreeView

Bernard Lessard 1

I'm using WPF .Net 9.0, I cannot see the SelectedItem element of the TreeView.

Anybody would know why ?

SelectedItem

1 answer

Your answer

Answer 1

Anonymous

Hi, @Bernard Lessard. Welcome to Microsoft Q&A.

You could get the SelectedItem of TreeView in code, refer to the following method:

MainWindow.xaml

<Grid>
 <TreeView x:Name="MyTreeView" SelectedItemChanged="TreeView_SelectedItemChanged"></TreeView>
</Grid>

MainWindow.xaml.cs

private void TreeView_SelectedItemChanged(object sender,RoutedPropertyChangedEventArgs<object> e)
{
     var item = MyTreeView.SelectedItem;
}

Also note that the SelectedItem of TreeView is a Get property, which could only be obtained but not set. It cannot be set, so SelectedItem doesn't make much sense in XAML, and as you could see, SelectedItem is not in XAML.

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Bernard Lessard 1 Reputation point

2025-02-17T16:39:05.2966667+00:00

But how can i set the treeview selection by code (programmatically)?

thanks

Anonymous

Hi, @Bernard Lessard.

Set TreeView selection: You could set TreeViewItem.IsSelected to true.

Refer to the following example: MainWindow.xaml

    <Grid>
        <TreeView x:Name="MyTreeView"  Loaded="MyTreeView_Loaded">
            <TreeView.ItemTemplate>
                <DataTemplate>
                    <Grid>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="50"/>
                            <ColumnDefinition Width="50"/>
                        </Grid.ColumnDefinitions>
                        <TextBlock Grid.Column="0" Text="{Binding Id}"></TextBlock>
                        <TextBlock Grid.Column="1" Text="{Binding Name}"></TextBlock>
                    </Grid>
                </DataTemplate>
            </TreeView.ItemTemplate>
        </TreeView>
    </Grid>

Person.cs

public class Person
{
    public int Id { get; set; }

    public string Name { get; set; }
}

MainWindow.xaml.cs

public partial class MainWindow : Window
{
    public ObservableCollection<Person> people = new ObservableCollection<Person>() {
        new Person(){ Id = 1,Name="AA"},
        new Person(){ Id = 2,Name="BB"},
        new Person(){ Id = 3,Name="CC"},
        new Person(){ Id = 4,Name="DD"},
    };

    public MainWindow()
    {
        InitializeComponent();
        MyTreeView.ItemsSource = people;
    }

    private void MyTreeView_Loaded(object sender, RoutedEventArgs e)
    {
        //Suppose you want to select this element
        var selectItem = new Person() { Id = 3, Name = "CC" };

        
        var treeViewItem = GetTreeViewItem(MyTreeView, selectItem);

        if(treeViewItem!=null)
        {
            treeViewItem.IsSelected = true;
        }
    }

    //Get the TreeViewItem of the corresponding element by comparing the ID
    public TreeViewItem GetTreeViewItem(ItemsControl parent, Person selectItem)
    {
        // Check the children of the parent
        foreach (var child in parent.Items)
        {

            var childContainer = parent.ItemContainerGenerator.ContainerFromItem(child) as TreeViewItem;
            if (childContainer == null)
                continue;

            // If this child is the one we are looking for, return it
            if (((Person)childContainer.DataContext).Id == selectItem.Id)
                return childContainer;

            // Otherwise, recursively check the child's children
            var result = GetTreeViewItem(childContainer, selectItem);
            if (result != null)
                return result;
        }

        // If no matching item was found, return null
        return null;
    }
}

enter image description here

You could also set IsSelected through property binding：WPF MVVM TreeView SelectedItem - Stack Overflow.

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Anonymous

2025-02-20T01:03:32.5333333+00:00

Hi, @Bernard Lessard.

Is there any update to the question? Did my answer solve your problem? If so, you could accept it as the answer. It's helpful for community members with related questions.
Bernard Lessard 1 Reputation point

2025-02-20T01:06:34.6966667+00:00

If so, How can I set the selected item by code ? thanks
Anonymous

2025-02-20T01:16:24.6366667+00:00

Hi, @Bernard Lessard.

Have you checked the code I provided? In my test results, by setting TreeViewItem.IsSelected to True, the Item could be successfully selected.
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Anonymous

2025-02-28T08:03:26.78+00:00

Hi, @Bernard Lessard.

Do you have any updates regarding the question? If my response resolved your issue, please consider marking it as the accepted answer. This will benefit other community members who have similar questions. If you still have problems, please describe the problem in more detail.

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WPF Cannot see SelectedItem in TreeView

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