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
 
 
 
 

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.

I have a TreeView declared and bound to a hierarchical database table. I'd like to be able to Cancel the 'Check' function on any node where HasChildren == true. I don't mind the check box being visible, because I like the multiple check states of the Parent Nodes, but the user should be only able to actually check the nodes where HasChildren == false. Is there a way to cancel the check for those parent nodes?

Please forward the ticket as a feature request for TreeView. For example:

<TelerikTreeView Data="@Data" CheckParents="true"CheckOnClick="true"CheckChildren="false" AllowParentNodesCheck="false">

The feature request is about introducing a configuration option about a delay to start the drag operation. Currently, the lack of such functionality causes unexpected drag clue appearance on double click. 

```
In my treeview the user can double-click to open an item or they can drag to reorganize the tree. When you double-click you can see the drag & drop initiates for the brief fraction of a second. Which is a confusing and unpleasant UX. It would be preferable if a drag & drop didn't initiate until the user dragged for 3-4 pixels from the mousedown location, as opposed to a single pixel. 

In general if there's a behavior like this that I would want to tweak, are there ways to adjust the control or override behaviors using Javascript? I used to do all sorts of stuff with the jQuery controls.

```

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)

---

Hi!

I can't find anything about validating drop targets. The only example in the demos checks the validity in the onDrop event. A bit late ...

Here are a few alternatives what will be useful for the TreeView to have:

1) new event OnDrag which fires when item is dragged over and dragged out of another item. Returns boolean indicating dropping is enabled. Requires a lot of roundtrips...

2) new properties of the TreeView items (DragType, DropTypes). Disables drop when DragType not in DropTypes.

3) a more generic DropZone component as in 2) which also could be used in TreeView templates.

https://chrissainty.com/investigating-drag-and-drop-with-blazor/ wrote an interesting article (sponsored by Telerik Blazor!) 

https://github.com/chrissainty/SimpleDragAndDropWithBlazor

Could be a inspiration for a generic DropZone component!

Best regards,
Jan

Hi everyone,

We created this item to request your feedback on how you use the treeview binding with regards to the Expanded state of the nodes.

At the moment, the treeview updates the field in the collection when an item gets expanded or collapsed, and that makes it unique in the suite - the other data bound components do not alter their data source silently, and this is the general pattern we want to follow in order to have consistency across the board.

Thus, there are several approaches we are considering and we want to get your take on how you would find this most comfortable:

• Keep the current situation where the treeview updates the ExpandedField in the Data silently [we would rather change it] - the Data collection gets changed automatically. To control an expanded item, prepare the data source accordingly.
• Use the OnExpand event to get the item and its new state in order to update the collection yourself if needed. If you don't use the field for anything but to control the state of the treeview, you will not need to change anything. To control an expanded item, prepare the data source accordingly when providing it to the treeview. If you will be reusing the same data source with alterations, you may have to handle the event to sync the state between the treeview and the data.
• Use an ExpandedItems collection [we are inclined to go with this approach at the moment] - this will be a collection that you can provide to the treeview separately from its data source, like the selected items in a grid. This will let you avoid an Expanded field in the data (which we believe may not be present in an actual database anyway) and you will be able to use business logic to determine which items to add/remove to that collection, this also includes nested levels, even added through load-on-demand.

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;
}

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.

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

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

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.

I need to be able to multiselect items in a treeview and drag n drop to reorder items.

(Same as RadTreeView AJAX component)

I would like a node click event exposed from the treeview.

At the moment, you need to use a template. Example and considerations are available in the following forum thread: https://www.telerik.com/forums/row-click-and-double-click-events#PQpO8DcbzkCArF3UqoLcWA.