I would like the TreeList to support row virtualization. It will be useful when working with large data.

I would like to start the tree grid with all rows collapsed. At the moment I can do this only through load on demand.

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I am using the Drag'N'Drop functionality of the Blazor TreeList and since the update to version 5.0.0 I cannot determine the destination component anymore, because the event argument parameter "DestinationComponentId" is always empty. I have assigned the ID of my TreeList components and everything worked well with version 4.6.0.

It does not matter whether I drag Items around within the same component or try to move them to another TreeList. The parameter is also empty when I try to drag items from a Grid to a TreeList.

Hello,

Here is your code of the example "how to load hierarchical data on demand" with the option FilterMode = "@ TreeListFilterMode.FilterMenu"
As you can see if we click on a node the whole hierarchy disappears. if you remove this option all work fine

 

@* this sample shows how to load hierarchical data on demand and one way of handling no data being returned. Depending on your models and data logic you may have to tweak some checks, review the code comments for details.

*@

<TelerikTreeList Data="@Data"
                 ItemsField="@(nameof(Employee.DirectReports))"
                 HasChildrenField="@(nameof(Employee.HasChildren))"
                 OnExpand="@OnExpandHandler"
                 Pageable="true" Width="550px" Height="400px" FilterMode="@TreeListFilterMode.FilterMenu" >
    <TreeListColumns>
        <TreeListColumn Field="Name" Expandable="true" Width="220px" />
        <TreeListColumn Field="HireDate" Width="120px" />
    </TreeListColumns>
</TelerikTreeList>

@code {
    public List<Employee> Data { get; set; }

    // load on demand through the event
    async Task OnExpandHandler(TreeListExpandEventArgs args)
    {
        Employee item = args.Item as Employee;
        if (item.HasChildren && // it is marked as having children
            (item.DirectReports == null || item.DirectReports.Count == 0) // there are no child items
            )
        {
            // request data
            var children = await GetChildren(item);

            if (children.Count > 0)
            {
                // child items exist - add them to the current item
                item.DirectReports = children;
            }
            else
            {
                // no nested data - hide the expand arrow
                item.HasChildren = false;
            }
        }
    }

    async Task<List<Employee>> GetChildren(Employee itm)
    {
        await Task.Delay(400); // simulate delay. Remove for a real app

        List<Employee> data = new List<Employee>();

        // to showcase an example of when no actual child items are returned
        // we will check for too long nesting chain with this simpe logic
        if (itm.Name.LastIndexOf("Child of") < 15)
        {
            data.Add(new Employee
            {
                Name = "Child of " + itm.Name,
                HasChildren = true
            });
        }

        return await Task.FromResult(data);
    }

    // sample model

    public class Employee
    {
        // hierarchical data collections
        public List<Employee> DirectReports { get; set; }
        public bool HasChildren { get; set; }

        // data fields for display
        public string Name { get; set; }
        public DateTime HireDate { get; set; }
    }

    // initial data generation

    protected override async Task OnInitializedAsync()
    {
        List<Employee> data = new List<Employee>();
        for (int i = 0; i < 6; i++)
        {
            data.Add(new Employee
            {
                Name = $"root: {i}",
                HireDate = DateTime.Now.AddYears(-i),
                HasChildren = true
            });
        }

        // mark an item as non-expandable (not having children)
        data[1].HasChildren = false;
        data[1].Name += "(not expandable) ";

        Data = data;
    }
}

It would be nice to have the same capabilities for working with TreeList columns as in the ColumnMenu for Grid. Espesially columns chooser. 

When I add a child to a node in the TreeList it would not render until I expand or collapse that node.

I would like a feature that exposes the same behavior as the CheckParents in the TreeView. 

I'd like to prevent the user from dropping a column at a certain position when reordering. Please expose an OnColumnReorder that I can cancel to stop the reordering operation in this case.

I am using the TreeList component with hierarchical data. The CheckBoxList allows filtering only by the root items, however, I want it to be hierarchical to support filtering by child records as well. 

Currently, the DisplayFormat attribute is applied only to the values displayed in the Grid, while the checkbox list filter options remain unaffected by this formatting.

The DisplayFormat attribute should also impact the checkbox list options, providing consistent formatting across the entire Grid.

Please add TreeList Export to Excel

Regards

Andrzej

Would it be possible to have the ability to create compact TreeList's similar to how we can now in a Grid? Since Size=ThemeConstants.Grid.Size.Small is available a Grid now it seems natural this would be a next step. If we can be provided with a work around for the time being that would be great.

Columns, which are added to the TreeList after the initial load, are not resizable.

I'm working on TreeList. Some of my columns will be rendered after the initial loading. I checked the code, seems you just set up column render right after the first time TreeList Header rendered. Mean the columns that will be rendered after the first-render time will not be resizable.

I'm using Telerik TreeList. I'm so happy that it supports Drag&Drop. But, if there are too many items on the list, it is really hard to drag an item from the top to the end of the list. The TreeList doesn't scroll the list automatically (Auto Scroll) when I drag an item to the edge of the TreeList.

Hello,

The scenario is:

1. Some filters are applied in OnStateInit
2. The user clears the filters from the Clear button in the filter menu.
3. The user opens the filter menu again and the checkboxes and textboxes look like the filters are still applied.

Test page: https://blazorrepl.telerik.com/cmasmAvk52l6Xckn02

This is a regression that occurred in version 3.2.0.

All of the above applies to the Grid component as well.

Currently, the TreeList CheckBox selection exposes an option to select the children if the parents are selected. Please also add support for CheckParents option similar to the one in the TreeView component. This will allow marking the parent as selected if its children are selected.

From what I can see, currently the only way to set the expanded items for a TreeList is through the state.

The main problem is that the state doesn't fire the OnExpand event, meaning that if you have a server loaded tree you need to make sure to load the data before each item is expanded. It also allows for duplicates in the 'ExpandedItems' if you don't check for duplicates before adding to it.

The TreeView has an 'ExpandedItems' parameter that can be bound which is a bit nicer than using the state, but from my quick test this also doesn't fire the OnExpand event.

 

My request is for one of the following to be added:

1. Similar to how you can set the 'HasChildrenField' or 'ItemsField' on the TreeList, allow a 'IsExpandedField' value to be bound (Should fire the OnExpand when changed if possible). This would be the simplest way allow bindable control over the expansion of items while also making it so we don't have to manage duplicates in the 'ExpandedItems' collection.
   
2. Expose a method to expand/unexpand rows. This would be different to manually changing the state as it would also fire the OnExpand event for each row expanded.
   
3. Similar to the TreeView, allow an 'ExpandedItems' to be bound. Preferably this would also fire the OnExpand event.

The TreeList should add an event OnDragStatus that would query the app during active dragging to determine if the current drag location is valid or not. If invalid, it could show the invalid drag icon:

This would give better feedback to the user during dragging.

Could you add this as a feature request please?

Not sure if this is a bug or missing feature, but when a user is actively doing drag and drop in the TreeList, the drag and drop should cancel as soon as they press 'Esc', just like in most apps. This is pretty standard behavior. Currently, pressing 'Esc' during drag and drop does not do anything.

If this is not a bug, could you please add this as a feature request?

Hello,

Please add support for sorting and filtering when the TreeList is data bound to a List<Dictionary> or ExpandoObject. Currently these data operations throw an exception System.ArgumentException: Invalid property or field

TreeList REPL page with Dictionary

TreeList REPL page with ExpandoObject