Expand treeview node when page is loaded

Question

Hi,I have a problem with programmatically expanding nodes by calling ExpandAll method when a list of nodes is populated from a HTTP request.  I have found a similar issue in thread https://www.syncfusion.com/forums/156397/expand-to-node-when-page-is-loaded. However, if I try to modify the example from the thread to simulate asynchronous HTTP request, the example stops working and nodes do not expand.  If I comment out the Task.Delay call it starts working again.Is there anything I can do on my side or is this a bug in Syncfusion library?Best regards,DavidAttachment: TreeExpanded1303825494_9037c658.zip

Prasanth Madhaiyan · Accepted Answer

Hi Ddrapela,Greetings from Syncfusion support.We have validated the reported query, and this has already
been considered as a bug at our end. The fix for this issue will be included in
our weekly patch release on August 30, 2022. You can track the status of the
issue fix using the following feedback link.Feedback: https://www.syncfusion.com/feedback/36839/expandallasync-is-not-working-with-dynamic-data-in-the-blazor-wasm-treeviewDisclaimer: Inclusion of this solution in the
weekly release may change due to other factors including but not limited to QA checks
and works reprioritization.Regards,Prasanth Madhaiyan.

Sivakumar ShunmugaSundaram · Answer

Hi Ddrapela,Thanks for your patience.On our further validation, the reported issue occurs due to
expanding the TreeView node using the ExpandAllAsync method in the
TreeView DataBound event. We would like to let you know that the
Treeview component is ready after the DataBound event, once we tried to
expand the node in that event, it executes before the component renders and
that is why the nodes are not expanded at the initial render. To overcome the
issue, we suggest you expand the TreeView nodes in the Blazor
OnAfterRenderAsync life cycle. Which is triggered after the component is ready
to render in the UI. We have attached the prepared sample for your reference.Refer to the below code snippet.

[Index.razor],

@code{
  ...
     
  protected override async Task OnInitializedAsync()
     
  {
         
  await base.OnInitializedAsync();
         
  await Task.Delay(100);//simulate http request
  ...
     
  protected override async Task
  OnAfterRenderAsync(bool firstRender)
     
  {
        
  if
  (!firstRender)
         
  {
         
  await treeView.ExpandAllAsync();

}
     
  }

}

Sample: https://www.syncfusion.com/downloads/support/directtrac/general/ze/TreeExpanded1303825494-762871418.zipPlease check the attached sample and get back to us if you
need any further assistance.Regards,Sivakumar S