AutoExpand treeview in WPF

Question

Is there a way to automatically expand all nodes from a treeview in WPF? I searched and didn't even find an expand function in the treeview property.

Thanks

Forgot to mention I don't have TreeviewItem, but different kinds of items in my tree. — David Brunelle, Sep 30 '09 at 13:05

Anvaka · Accepted Answer · 2013-07-26T06:21:36.480

You can set ItemContainerStyle and use IsExpanded property.

<Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
   <Grid>
      <TreeView>
         <TreeView.ItemContainerStyle>
            <Style TargetType="{x:Type TreeViewItem}">
               <Setter Property="IsExpanded" Value="True"/>
            </Style>
         </TreeView.ItemContainerStyle>
         <TreeViewItem Header="Header 1">
            <TreeViewItem Header="Sub Item 1"/>
         </TreeViewItem>
         <TreeViewItem Header="Header 2">
            <TreeViewItem Header="Sub Item 2"/>
         </TreeViewItem>
      </TreeView>
   </Grid>
</Page>

If you need to do this from code, you can write viewmodel for your tree view items, and bind IsExpanded property to corresponding one from model. For more examples refer to great article from Josh Smith on CodeProject: Simplifying the WPF TreeView by Using the ViewModel Pattern

I used this method for MVVM bound view and it worked perfectly. — Roddles, Jul 17 '19 at 01:31

score 5 · Answer 2 · edited Apr 28 '14 at 05:56

5

This is what I use:

private void ExpandAllNodes(TreeViewItem rootItem)
{
    foreach (object item in rootItem.Items)
    {
        TreeViewItem treeItem = (TreeViewItem)item;

        if (treeItem != null)
        {
            ExpandAllNodes(treeItem);
            treeItem.IsExpanded = true;
        }
    }
}

In order for it to work you must call this method in a foreach loop for the root node:

// this loop expands all nodes
foreach (object item in myTreeView.Items)
{
    TreeViewItem treeItem = (TreeViewItem)item;

    if (treeItem != null)
    {
        ExpandAllNodes(treeItem);
        treeItem.IsExpanded = true;
    }
}

edited Apr 28 '14 at 05:56

Fedor

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answered Sep 28 '09 at 15:27

Carlo

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3

Hi Carlo. This will not work if you have something different from TreeViewItem in your Items collection. If you want to be sure this approach works in any case, you should use ItemContainerGenerator from your TreeView object and call it's ContainerFromItem() method. – Anvaka Sep 28 '09 at 15:31
You are right, the way I add the items to my treeview is myTree.Items.Add(new TreeViewItem() { Header = myObject });, That's why it works for me. Sorry for misleading. – Carlo Sep 28 '09 at 16:22
1

You can simplify the code to be myTreeView.Items.OfType() and you will not have to check for null or case the items. – jwize Apr 03 '14 at 19:09

score 5 · Answer 3 · answered Jun 04 '14 at 18:44

if you want expand manually you can try

Xaml:

<TreeView x:Name="TreePeople">
    <TreeView.ItemContainerStyle>
        <Style TargetType="{x:Type TreeViewItem}">
            <Setter Property="IsExpanded" Value="True" />
        </Style>
    </TreeView.ItemContainerStyle>
</TreeView>

c#:

bool Expanded = false; 
// The event subscription method (for a button click)
private void ButtonExpand__Click(object sender, RoutedEventArgs e)
{
    Expanded = !Expanded;
    Style Style = new Style
    {
        TargetType = typeof(TreeViewItem)
    };

    Style.Setters.Add(new Setter(TreeViewItem.IsExpandedProperty, Expanded));
    TreePeople.ItemContainerStyle = Style;
}

jwize · Answer 4 · 2014-04-03T22:49:02.300

2

Carlo's answer was better because it opens all levels

This improves upon that example with a little more concise code example.

    private void ExpandAllNodes(TreeViewItem treeItem)
    {
        treeItem.IsExpanded = true;  
        foreach (var childItem in treeItem.Items.OfType<TreeViewItem>())
        {
                ExpandAllNodes(childItem);
        }
    }

Call it by using this line of code

TreeViewInstance.Items.OfType<TreeViewItem>().ToList().ForEach(ExpandAllNodes);

edited Apr 03 '14 at 22:49

answered Apr 03 '14 at 19:17

jwize

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`foreach (TreeViewItem childItem in TreeItem.Items)` is shorter than your foreach but works just as fine. :) – Shakaron Jul 16 '15 at 14:55
1

This won't work when using MVVM because the items won't be `TreeViewItem`. See Anvaka's comment on Carlo's answer. – Oct 29 '15 at 07:41

score 0 · Answer 5 · answered May 20 '19 at 14:20

0

Another programmatical way to manipulate full expansion of tree items, maybe via c# code, is using the TreeViewItem.ExpandSubTree() command on a root node.

private void ExpandFirstRootNode()
{
   TreeViewControl.Items[0].ExpandSubtree();
}

answered May 20 '19 at 14:20

gmmarcilli

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Wouldn't this only expand 1 `Items` sub tree? Shouldn't we do all? – Derek Pollard May 20 '19 at 14:44

AutoExpand treeview in WPF

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