Questions on UI for Blazor Forum

0 answers

32 views

Using the TelerikTreeView component inside the TelerikWindow component

Hi all,

When TelerikTreeView is used within TelerikWindow's WindowContent, mouse hover events trigger continuous re-rendering of the entire window content, resulting in significant performance degradation. However, using TelerikTreeView directly on a page outside the window doesn't cause these re-rendering issues.

<TelerikWindow Visible=true>
    <WindowContent>
            <TelerikTreeView Data="@TreeData">
                <TreeViewBindings>
                    <TreeViewBinding>
                        <ItemTemplate>
                            @{
                                TreeItem itm = context as TreeItem;
                                <span @onclick="@( _ => NodeClick(itm) )">
                                    Node:
                                    <strong>@itm.Text</strong>
                                </span>
                            }
                        </ItemTemplate>
                    </TreeViewBinding>
                </TreeViewBindings>
            </TelerikTreeView>
    </WindowContent>
</TelerikWindow>

@code {
    string result { get; set; }
    async Task NodeClick(TreeItem clickeNode)
    {
        result = $"Last clicked node Id: {clickeNode.Id}";
    }

    // sample data

    public IEnumerable<TreeItem> TreeData { get; set; }

    public class TreeItem
    {
        public string Text { get; set; }
        public int Id { get; set; }
        public List<TreeItem> Items { get; set; } = new List<TreeItem>();
        public bool HasChildren { get; set; }
    }

    protected override void OnInitialized()
    {
        LoadHierarchical();
    }

    private void LoadHierarchical()
    {
        List<TreeItem> roots = new List<TreeItem>() {
            new TreeItem { Text = "Item 1", Id = 1, HasChildren = true },
            new TreeItem { Text = "Item 2", Id = 2, HasChildren = true }
        };

        roots[0].Items.Add(new TreeItem
        {
            Text = "Item 1 first child",
            Id = 3

        });

        roots[0].Items.Add(new TreeItem
        {
            Text = "Item 1 second child",
            Id = 4

        });

        roots[1].Items.Add(new TreeItem
        {
            Text = "Item 2 first child",
            Id = 5

        });

        roots[1].Items.Add(new TreeItem
        {
            Text = "Item 2 second child",
            Id = 6

        });

        TreeData = roots;
    }
}

TreeView

Window

updated question on 18 Nov 2025

1 answer

106 views

Dropdownlist with Treeview

Hello, i want use the treeview, i have many elements. so it stretch if i expand it over the screen, and this is not fine :)

so i want the treeview in the dropdown list. but it doestn work. it looks horrible. Have someone a idea or a soution. thank you.

this is my code. and i need a treeview. because i have expand items.

DropDownList

TreeView

answered on 24 Feb 2025

0 answers

51 views

TelerikTreeView can no longer expand single nodes since v7

Hello,

We recently upgraded to Telerik v7.0 for our controls and since then expanding a single item always expands all items. Has anyone else run into this or does anyone know a workaround?

TreeView

asked on 29 Jan 2025

1 answer

88 views

Switch instead of checkbox in TreeView

Is there a way to use a Switch control instead of checkbox in a TreeView? I am able to use ItemTemplate to insert a switch next to the checkbox but I need to replace the checkbox and have the switch use CheckChildren and CheckParents.

Any ideas?

Thanks!


<TelerikTreeView OnItemRender="@OnItemRender" CheckBoxMode="TreeViewCheckBoxMode.Multiple" CheckChildren="true" CheckParents="true" Data="@FlatData" @bind-ExpandedItems="@ExpandedItems">
    <TreeViewBindings>
        <TreeViewBinding TextField="Text" IdField="Id" ParentIdField="ParentId" ItemsField="Text" HasChildrenField="HasChildren" IconField="Icon">
            <ItemTemplate>
                @{var treeItem = (TreeItem)context; }
                <div class="treeview-item">
                    <TelerikSwitch @bind-Value="treeItem.IsChecked" />
                    <span>@treeItem.Text</span>
                </div>
            </ItemTemplate>
        </TreeViewBinding>
    </TreeViewBindings>
</TelerikTreeView>

Switch

TreeView

answered on 02 Jan 2025

1 answer

327 views

TreeView Disposing/Error

In my blazor app I'm seeing the TelerikTreeView is erroring out during garbage collection or disposing when I switching between pages too quickly in my. Is there something I can do to suppress this error or add some nullcheck so this doesnt appear in my logs?

Here is the error I'm getting:

Microsoft.JSInterop.JSException: Cannot read properties of null (reading 'addEventListener') TypeError: Cannot read properties of null (reading 'addEventListener') at c.bindEvents (https://0.0.0.0/_content/Telerik.UI.for.Blazor/js/telerik-blazor.js:50:1282242) at new c (https://0.0.0.0/_content/Telerik.UI.for.Blazor/js/telerik-blazor.js:50:1282116) at e.initComponent (https://0.0.0.0/_content/Telerik.UI.for.Blazor/js/telerik-blazor.js:50:1085487) at e.initTreeView (https://0.0.0.0/_content/Telerik.UI.for.Blazor/js/telerik-blazor.js:50:1279920) at https://0.0.0.0/_framework/blazor.webview.js:1:3337 at new Promise (<anonymous>) at beginInvokeJSFromDotNet (https://0.0.0.0/_framework/blazor.webview.js:1:3311) at https://0.0.0.0/_framework/blazor.webview.js:1:42795 at EventTarget.<anonymous> (<anonymous>:7:62) at EmbeddedBrowserWebView.<anonymous> (<anonymous>:1:40673)
at Microsoft.JSInterop.JSRuntime.InvokeAsync[TValue](Int64 targetInstanceId, String identifier, Object[] args)
at Microsoft.JSInterop.JSRuntimeExtensions.InvokeVoidAsync(IJSRuntime jsRuntime, String identifier, Object[] args)
at Telerik.Blazor.Components.TelerikTreeView.InitTreeView()
at Telerik.Blazor.Components.TelerikTreeView.OnAfterRenderAsync(Boolean firstRender)
at Microsoft.AspNetCore.Components.RenderTree.Renderer.GetErrorHandledTask(Task taskToHandle, ComponentState owningComponentState)
Microsoft.JSInterop.JSException: Cannot read properties of null (reading 'addEventListener') TypeError: Cannot read properties of null (reading 'addEventListener') at c.bindEvents (https://0.0.0.0/_content/Telerik.UI.for.Blazor/js/telerik-blazor.js:50:1282242) at new c (https://0.0.0.0/_content/Telerik.UI.for.Blazor/js/telerik-blazor.js:50:1282116) at e.initComponent (https://0.0.0.0/_content/Telerik.UI.for.Blazor/js/telerik-blazor.js:50:1085487) at e.initTreeView (https://0.0.0.0/_content/Telerik.UI.for.Blazor/js/telerik-blazor.js:50:1279920) at https://0.0.0.0/_framework/blazor.webview.js:1:3337 at new Promise (<anonymous>) at beginInvokeJSFromDotNet (https://0.0.0.0/_framework/blazor.webview.js:1:3311) at https://0.0.0.0/_framework/blazor.webview.js:1:42795 at EventTarget.<anonymous> (<anonymous>:7:62) at EmbeddedBrowserWebView.<anonymous> (<anonymous>:1:40673)
at Microsoft.JSInterop.JSRuntime.InvokeAsync[TValue](Int64 targetInstanceId, String identifier, Object[] args)
at Microsoft.JSInterop.JSRuntimeExtensions.InvokeVoidAsync(IJSRuntime jsRuntime, String identifier, Object[] args)
at Telerik.Blazor.Components.TelerikTreeView.InitTreeView()
at Telerik.Blazor.Components.TelerikTreeView.OnAfterRenderAsync(Boolean firstRender)
at Microsoft.AspNetCore.Components.RenderTree.Renderer.GetErrorHandledTask(Task taskToHandle, ComponentState owningComponentState)

TreeView

updated answer on 15 Nov 2024

1 answer

105 views

Drag and Drop in Treeview

Hi, I am trying to implement Drag and Drop on the Blazor Treeview component. I am using version 4.4.0 and have been referencing this documentation: https://docs.telerik.com/blazor-ui/components/treeview/drag-drop#ondragstart-event

So far

The event "OnDragStart" does not exist,The class "TreeViewDragStartEventArgs" does not exist.

Your documentation never seems to list when functionality is available so I have no idea if it is the version I am using, something I have done, or your components.
Would love some help clearing this up.

TreeView

answered on 30 Sep 2024

1 answer

81 views

TreeView with checkboxes: Initial value for parent nodes

Hi,

I have a TreeView where the initial values are set programmatically.

When all the child nodes are checked the parent node should be checked as well. But it isn't:
https://blazorrepl.telerik.com/GIOLlWks03IKIiiZ31

Is there any solution for that?

Best regards,

Rayko

TreeView

answered on 19 Jul 2024

1 answer

92 views

Treeview with checkboxes, problems with CheckParents=@true CheckChildren=@true

We are updating the data bound to the treeview dynamically which has CheckParents and CheckChildren set to true . Issue is it appears the binding is ignoring these flags. screenshot show it ignoring CheckParents. This REPL shows it ignoring CheckChildren https://blazorrepl.telerik.com/GyuKmVPY13f8gREi18