TreeListAllowedDropTarget Enum

Lists values that specify allowed drag-and-drop targets.

Namespace: DevExpress.Blazor

Assembly: DevExpress.Blazor.Grid.v26.1.dll

NuGet Package: DevExpress.Blazor

Declaration

public enum TreeListAllowedDropTarget

Members

Name	Description
None	Users cannot reorder rows or drop them onto this TreeList from another component.
Internal	Users can reorder rows within this TreeList.
External	Users can drop rows onto other components.
All	Users can reorder rows within this TreeList and drop them onto other components.

Related API Members

The following properties accept/return TreeListAllowedDropTarget values:

• DxTreeList.AllowedDropTarget
• ITreeList.AllowedDropTarget

Remarks

In the following example, the Grid allows users to drag rows to external targets. The TreeList accepts rows from the Grid and allows row reordering:

Run Demo: Drag and Drop Rows - Between Components

@inject IEmployeeTaskDataProvider EmployeeTaskDataProvider
<div class="components-container">
    <DxTreeList @ref="PlannedTasksTreeList"
                Data="PlannedTasks"
                KeyFieldName="Id"
                ParentKeyFieldName="ParentId"
                AllowSort="false"
                AutoExpandAllNodes="true"
                AllowDragRows="true"
                AllowedDropTarget="TreeListAllowedDropTarget.All"
                VirtualScrollingEnabled="true"
                SizeMode="Params.SizeMode"
                ItemsDropped="TreeList_ItemsDropped">
        <Columns>
            <DxTreeListDataColumn @ref="TreeList_NameDataColumn" FieldName="Name" Caption="Task" />
            <DxTreeListDataColumn FieldName="Priority" Width="100px" CaptionAlignment="TreeListTextAlignment.Center" TextAlignment="TreeListTextAlignment.Center">
                <CellDisplayTemplate>
                    @DemoTemplateIconUtils.GetEmployeeTaskPriorityIconHtml((EmployeeTask)context.DataItem)
                </CellDisplayTemplate>
            </DxTreeListDataColumn>
        </Columns>
        <DragHintTextTemplate>
            @if(context.DataItems[0] != null) {
                <span class="dxbl-text">@context.GetDisplayText(TreeList_NameDataColumn)</span>
                <span class="dxbl-text">@DemoTemplateIconUtils.GetEmployeeTaskPriorityIconHtml((EmployeeTask)context.DataItems[0])</span>
            }
        </DragHintTextTemplate>
        <ToolbarTemplate>
            <DxToolbar Title="Planned Tasks" />
        </ToolbarTemplate>
    </DxTreeList>

    <DxGrid Data="PendingTasks"
            AllowSelectRowByClick="true"
            SelectionMode="GridSelectionMode.Multiple"
            TextWrapEnabled="false"
            AllowDragRows="true"
            AllowedDropTarget="GridAllowedDropTarget.All"
            VirtualScrollingEnabled="true"
            SizeMode="Params.SizeMode"
            ItemsDropped="Grid_ItemsDropped">
        <Columns>
            <DxGridSelectionColumn Width="40px" />
            <DxGridDataColumn @ref="Grid_NameDataColumn" FieldName="Name" Caption="Task" />
            <DxGridDataColumn FieldName="Priority" Width="100px" CaptionAlignment="GridTextAlignment.Center" TextAlignment="GridTextAlignment.Center">
                <CellDisplayTemplate>
                    @DemoTemplateIconUtils.GetEmployeeTaskPriorityIconHtml((EmployeeTask)context.DataItem)
                </CellDisplayTemplate>
            </DxGridDataColumn>
        </Columns>
        <DragHintTextTemplate>
            @if(context.DataItems.Count == 1) {
                <span class="dxbl-text">@context.GetDisplayText(Grid_NameDataColumn)</span>
                <span class="dxbl-text">@DemoTemplateIconUtils.GetEmployeeTaskPriorityIconHtml((EmployeeTask)context.DataItems[0])</span>
            }
            else {
                <span class="dxbl-text">@(context.DataItems.Count) tasks</span>
            }
        </DragHintTextTemplate>
        <ToolbarTemplate>
            <DxToolbar Title="Pending Tasks" />
        </ToolbarTemplate>
    </DxGrid>
</div>

@code {
    ITreeList PlannedTasksTreeList { get; set; }

    DxTreeListDataColumn TreeList_NameDataColumn { get; set; }
    DxGridDataColumn Grid_NameDataColumn { get; set; }

    ObservableCollection<EmployeeTask> PlannedTasks { get; set; }
    ObservableCollection<EmployeeTask> PendingTasks { get; set; }

    protected override void OnInitialized() {
        var employeeTasks = EmployeeTaskDataProvider.GenerateData();
        PendingTasks = new ObservableCollection<EmployeeTask>(employeeTasks.Where(t => t.Priority > 0));
        var pendingTaskIds = PendingTasks.Select(t => t.Id).ToHashSet();
        PlannedTasks = new ObservableCollection<EmployeeTask>(employeeTasks.Where(t => t.Priority <= 0 && !pendingTaskIds.Contains(t.ParentId)));
    }

    void TreeList_ItemsDropped(TreeListItemsDroppedEventArgs evt) {
        var sourceTasks = GetTaskCollection(evt.SourceComponent);
        RemoveDroppedItems(sourceTasks, evt.DroppedItems);

        var targetTask = (EmployeeTask)evt.TargetItem;
        var index = targetTask != null
            ? PlannedTasks.IndexOf(targetTask) + (evt.DropPosition == TreeListItemDropPosition.After ? 1 : 0)
            : PlannedTasks.Count;

        var droppedTasks = evt.DroppedItems.OfType<EmployeeTask>();
        foreach(var droppedTask in droppedTasks) {
            droppedTask.ParentId = evt.DropPosition == TreeListItemDropPosition.Inside
                ? targetTask.Id
                : targetTask.ParentId;
        }

        InsertDroppedItems(PlannedTasks, evt.DroppedItems, index);
    }

    void Grid_ItemsDropped(GridItemsDroppedEventArgs evt) {
        var sourceTasks = GetTaskCollection(evt.SourceComponent);
        RemoveDroppedItems(sourceTasks, evt.DroppedItems);

        var targetTask = (EmployeeTask)evt.TargetItem;
        var index = targetTask != null
            ? PendingTasks.IndexOf(targetTask) + (evt.DropPosition == GridItemDropPosition.After ? 1 : 0)
            : PendingTasks.Count;

        InsertDroppedItems(PendingTasks, evt.DroppedItems, index);
    }

    void RemoveDroppedItems(IList<EmployeeTask> employeeTasks, IEnumerable<object> droppedItems) {
        foreach(var item in droppedItems)
            employeeTasks.Remove((EmployeeTask)item);
    }

    void InsertDroppedItems(IList<EmployeeTask> employeeTasks, IEnumerable<object> droppedItems, int index) {
        foreach(var item in droppedItems.Reverse())
            employeeTasks.Insert(index, (EmployeeTask)item);
    }

    ObservableCollection<EmployeeTask> GetTaskCollection(object grid) {
        return grid == PlannedTasksTreeList ? PlannedTasks : PendingTasks;
    }
}