Wpf treeview is not expanding correctly for the first time. It is working if loading again in same life cycle

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Hi,
i am trying to expand xml tree to first level in wpf, iam using attached property for this.

i am facing problem when i am loading xml fo r the first time at that time ,

here for first time " uiElement.ItemContainerGenerator.ContainerFromItem() " is returning null ,but on same life cycle if i try to load xml this property is working properly.

TreeViewItem treeItem = uiElement.ItemContainerGenerator.ContainerFromItem(item) as TreeViewItem;

can any one help me.

What I have tried:

this below line is giving null , this funtion is null ContainerFromItem for the first time

TreeViewItem treeItem = uiElement.ItemContainerGenerator.ContainerFromItem(item) as TreeViewItem

private static void OnTreeviewPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
try
{
TreeView uiElement = (TreeView)d;
uiElement.UpdateLayout();
TreeViewItem ti = GetItemFromObject(uiElement);

foreach (object item in uiElement.Items)
{

TreeViewItem treeItem = uiElement.ItemContainerGenerator.ContainerFromItem(item) as TreeViewItem;

if (treeItem != null)
{
// ExpandAll(treeItem, true);
treeItem.IsExpanded = true;
}

}

}
catch
{

}

}

view: treeview is inside a tab

<window x:class="WpfApplication3.MainWindow" xmlns:x="#unknown">
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<grid>
<tabcontrol>
<tabitem>
<treeview name="xmlTree"> HorizontalAlignment="Stretch"
VerticalAlignment="Stretch"
ItemTemplate= "{StaticResource NodeTemplate}"
ItemsSource="{Binding xmldocumrnt, Mode=OneWay, NotifyOnSourceUpdated=True, UpdateSourceTrigger=PropertyChanged}"
VirtualizingStackPanel.IsVirtualizing="False"
VirtualizingStackPanel.VirtualizationMode="Recycling"
Vm:ExpandXML.OpenXML="{Binding ISXmlExpand,UpdateSourceTrigger=PropertyChanged,NotifyOnSourceUpdated=True,Mode=TwoWay}" >
<treeview.itemcontainerstyle> <Style TargetType="{x:Type TreeViewItem}">
<setter property="FontSize" value="12">

</Style>

Posted 4-Jun-16 10:25am

kumar9avinash

Updated 28-Jul-16 3:18am

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Comments

Sergey Alexandrovich Kryukov 4-Jun-16 23:09pm

Please use the debugger and see where the line expanding the node is executed, check up if it happens at all or not.
You did not show where the function OnTreeviewPropertyChanged is called.

In other words, do appropriate debugging work. When and if you find out what's going on, in case you still don't see how to fix the code, provide more comprehensive information based on your observations. Ideally, you could write some simplified test code focusing only on one problem; then it can be made small enough to show 100% of code. Please see: SSCCE.

—SA

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mauryasantosh · Answer 1 · 2016-07-28T03:18:00

XML

Hi Avinesh,

 
you can try to add Setter property="IsExpended" value="True".
please find below code as Reference.......  


<TreeView Name="TreeView" BorderThickness="0" Foreground="Black" >
                                <TreeView.ItemContainerStyle>
                                    <Style TargetType="{x:Type TreeViewItem}">
                                        <Setter Property="IsExpanded" Value="True" />
                                    </Style>
                                </TreeView.ItemContainerStyle>

Please vote if it helpful .