It would be great to be able to expand nodes dynamically by setting the expand property by code.

protected async Task OnItemClickHandler(TreeViewItemClickEventArgs e)
{
    var item = e.Item as TreeViewItem;
    item.Expanded = true;
}

Hi.

I'd like to request the ability to set the Enabled property on check boxes in the treeview.

For example, given a tree view with check boxes:

<TelerikTreeView Data="@StorageItems"
                 @bind-CheckedItems="@CheckedItems"
                 CheckBoxMode="TreeViewCheckBoxMode.Multiple"
                 CheckParents="true"
                 CheckChildren="true" />

I'd like to make the tree view read-only so the check boxes appear disabled and the user cannot check-mark or uncheck-mark them.

Thank you.

The TreeView has CheckBoxMode="@TreeViewCheckBoxMode.Multiple" and CheckParents="true". Only some checkboxes are checked and there are parent checkboxes in indeterminate state.

When I try to clear all checked checkboxes, the indeterminate checkboxes are not cleared and maintain their state.

ADMIT EDIT:

Initially, this bug report was about unchecking all child items. However, it appears that the opposite behavior exists too - if all children are checked programmatically, the parent checkbox will show as indeterminate. In this case, check the parent explicitly as well.

Seems even having multiple selections we just can drag and drop items one by one, am I right? Basically having access to selected items & drop event I can code workaround & move them myself, but hope that we have it out of the box, do we?

Set TreeView selection type to multiple, select several items, try to drag, just one item will be dragged despite having several selected.

------------ADMIN EDIT--------------

A possible workaround can be implemented by using the OnDrop event when you have Multiple selected Items.

Stack trace:

crit: Microsoft.AspNetCore.Components.WebAssembly.Rendering.WebAssemblyRenderer[100]
      Unhandled exception rendering component: Unknown edit type: 0
      Error: Unknown edit type: 0
          at e.applyEdits (https://localhost:44363/_framework/blazor.webassembly.js:1:15008)
          at e.updateComponent (https://localhost:44363/_framework/blazor.webassembly.js:1:12880)
          at Object.t.renderBatch (https://localhost:44363/_framework/blazor.webassembly.js:1:1704)
          at Object.window.Blazor._internal.renderBatch (https://localhost:44363/_framework/blazor.webassembly.js:1:34784)
          at _mono_wasm_invoke_js_unmarshalled (https://localhost:44363/_framework/wasm/dotnet.3.2.0.js:1:172099)
          at wasm_invoke_iiiiii (<anonymous>:wasm-function[3160]:0x9b33d)
          at icall_trampoline_dispatch (<anonymous>:wasm-function[5777]:0xfe711)
          at mono_wasm_interp_to_native_trampoline (<anonymous>:wasm-function[4607]:0xca81d)
          at ves_pinvoke_method (<anonymous>:wasm-function[3209]:0x9cd40)
          at interp_exec_method (<anonymous>:wasm-function[1120]:0x2598d)
Microsoft.JSInterop.JSException: Unknown edit type: 0
Error: Unknown edit type: 0
    at e.applyEdits (https://localhost:44363/_framework/blazor.webassembly.js:1:15008)
    at e.updateComponent (https://localhost:44363/_framework/blazor.webassembly.js:1:12880)
    at Object.t.renderBatch (https://localhost:44363/_framework/blazor.webassembly.js:1:1704)
    at Object.window.Blazor._internal.renderBatch (https://localhost:44363/_framework/blazor.webassembly.js:1:34784)
    at _mono_wasm_invoke_js_unmarshalled (https://localhost:44363/_framework/wasm/dotnet.3.2.0.js:1:172099)
    at wasm_invoke_iiiiii (<anonymous>:wasm-function[3160]:0x9b33d)
    at icall_trampoline_dispatch (<anonymous>:wasm-function[5777]:0xfe711)
    at mono_wasm_interp_to_native_trampoline (<anonymous>:wasm-function[4607]:0xca81d)
    at ves_pinvoke_method (<anonymous>:wasm-function[3209]:0x9cd40)
    at interp_exec_method (<anonymous>:wasm-function[1120]:0x2598d)
  at Microsoft.JSInterop.WebAssembly.WebAssemblyJSRuntime.InvokeUnmarshalled[T0,T1,T2,TResult] (System.String identifier, T0 arg0, T1 arg1, T2 arg2) <0x3ae01e8 + 0x00046> in <filename unknown>:0 
  at Microsoft.JSInterop.WebAssembly.WebAssemblyJSRuntime.InvokeUnmarshalled[T0,T1,TResult] (System.String identifier, T0 arg0, T1 arg1) <0x3ae0108 + 0x00014> in <filename unknown>:0 
  at Microsoft.AspNetCore.Components.WebAssembly.Rendering.WebAssemblyRenderer.UpdateDisplayAsync (Microsoft.AspNetCore.Components.RenderTree.RenderBatch& batch) <0x3ae0010 + 0x0001e> in <filename unknown>:0 
  at Microsoft.AspNetCore.Components.RenderTree.Renderer.ProcessRenderQueue () <0x387e448 + 0x000f2> in <filename unknown>:0

Currently there does not appear to be a way to provide validation of the drag & drop action prior to the OnDrop hook. The result is that the user experience looks as if they are able to drag and drop nodes to places where they should not be able to based on custom logic. It appears there is some logic behind the scenes that provide an icon during the hover of the drag and drop action but the logic determining this icon is not extendable to my knowledge. What I'd like to be able to do is override or extend the logic determines on hover UI feedback of the drag and drop action.  Specifically, for my case, I would like to be able to validate with business logic if the drag and drop action is allowed prior to the OnDrop so invalid actions look something like the below picture. This picture from your demo site shows the feedback provided when you try to drag and drop a node onto itself. It shows a clear icon that suggest the action is not allowed but as I mentioned the logic to produce this result does not appear to be extensible.

The TreeView should automatically update when a change in data fields occur. Changes in the `ItemsField`, `HasChildren` are crucial to be tracked to allow easy manipulation of data in binding to hierarchical data. This request will fulfill the observable collection support of the TreeView.

---

ADMIN EDIT

Changes in the ExpandedField of the element have been previously handled in the TreeView. However, this has been a side effect of incorrect code in our component that was causing performance hit. We reviewed our component and how it could provide better coverage in user scenarios, so here are our steps:

- Implement tracking of data item changes with ObservableCollection, so that we could fully support binding to observable data - click the Vote and Follow buttons on the current page to raise the priority of this feature implementation and to get notified for status updates.



We've been evaluating a major change where the ExpandedItems to be controlled via parameter/state. So, we would really appreciate if you could share feedback whether this change would be good for your project and use case.

- Implementation of ExpandedItems in TreeView to substitute ExpandedField in the collection: https://feedback.telerik.com/blazor/1448095-expanded-items-handling-feedback-requested

We believe that the above steps are the way to go with the maturing of the TreeView component.

A workaround could be reinitializing the Data when you update the property of the item, that will force the treeview to update:

TreeViewData = new List<MyModel>(TreeViewData)

---

If i collapse/expand any item of treeview then each item of collapsed/expanded branch will be rendered twice.

Clicking in or away from the treeview re-renders all nodes too.

The issue manifests both when

• using .Add() or .Remove() on an ObservableCollection
• creating a new List<T>(updatedData)

Happens in 2.14.1 first.

*** Thread created by admin on customer behalf ***

Add checkbox support at the node level.  Similar to...

https://www.telerik.com/kendo-angular-ui/components/treeview/checkboxes/

Hi,

Is there a plan to support lines between treeview items as available in radtreeview?

radTreeView1.ShowLines = true;
radTreeView1.LineStyle = TreeLineStyle.DashDot;
 
Without this it is very confusing to the end user what the connections between open items are.
 
Regards,

peter