CODEWITHSUNDEEP
c#wpf
3xGuy
3xGuy

Reputation: 2559

TreeViewItem expanded event

Hello I am working with a WPF application where I am wanting to have an event fire before I expand an item on a TreeView. I know that there isn't an event already for this but I am not sure how to add one the way that I am doing this so any help will be appreciated.

here is the xaml.

 <TreeView x:Name="TreeView" Margin="20">
        <TreeView.Resources>
              <Style TargetType="{x:Type TreeViewItem}">
                   <!-- Some style -->
              </Style>
              <DataTemplate DataType="{x:Type models:DirectoryPathItem}">
                   <!-- some template -->
              </DataTemplate>
        </TreeView.Resources>
 </TreeView>

I am loading in code behind.

    private void LoadBaseDirectories()
    {
        var directoryInfo = new DirectoryInfo(@"C:\");

        var directories = directoryInfo.GetDirectories();

        foreach (var directory in directories)
        {
            TreeView.Items.Add(new DirectoryPathItem()
            {
                Children = new ObservableCollection<PathItem>(),
                Path = directory.FullName,
                Header = directory.Name
            });
        }
    }

Is there a way that I can call an event before expanding the TreeViewItem so I can load the children?

Upvotes: 2

Views: 287

Answers (1)

Joel Bourbonnais
Joel Bourbonnais

Reputation: 2718

Loading the children items before you actually expand may result in an unresponsive UI where the user does not understand why the list is empty.

I would suggest adding an item which represent the background task (i.g.: a loading spinner of some sort) and add proper items as soon as they are discovered.

Once done you may remove the loading spinner item.

This way, you won't need a new event and the user will understand what is going on.

Upvotes: 1

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