Drag and Drop in Blazor TreeView Component

13 Oct 20219 minutes to read

The Blazor TreeView component allows to drag and drop any node by setting AllowDragAndDrop  to true. Nodes can be dragged and dropped at all levels of the same TreeView.

The dragged nodes can be dropped at any level by indicator lines with line, plus/minus, and restrict icons. It represents the exact position where the node is to be dropped as sibling or child.

The following table explains the usage of indicator icons.

Icons	Description
Plus icon	Indicates that the dragged node is to be added as a child of target node.
Minus or restrict icon	Indicates that the dragged node is not to be dropped at the hovered region.
In between icon	Indicates that the dragged node is to be added as siblings of hovered region.

• In order to prevent dragging action for a particular node, the OnNodeDragStart event can be used which is triggered when the node drag is started. The OnNodeDragged event is triggered when the drag is stopped.

• The NodeDropped event is triggered when the TreeView node is dropped on the target element successfully.

In the OnNodeDragged event currently there is no option to cancel the event. However the other event arguments could be accessed.

@using Syncfusion.Blazor.Navigations
<SfTreeView TValue="TeamDetails" AllowDragAndDrop="true">
    <TreeViewFieldsSettings TValue="TeamDetails" Id="Id" Text="Name" Child="Children" DataSource="@Team" Expanded="Expanded"></TreeViewFieldsSettings>
</SfTreeView>

@code{
    public class TeamDetails
    {
        public string Id { get; set; }
        public string Name { get; set; }
        public bool Expanded { get; set; }
        public bool Selected { get; set; }
        public List<TeamDetails> Children;
    }
    List<TeamDetails> Team = new List<TeamDetails>();

    protected override void OnInitialized()
    {
        base.OnInitialized();
        List<TeamDetails> EmployeeDetails = new List<TeamDetails>();
        Team.Add(new TeamDetails
        {
            Id = "01",
            Name = "ASP.NET MVC Team",
            Expanded = true,
            Children = EmployeeDetails,
        });
        EmployeeDetails.Add(new TeamDetails
        {
            Id = "01-01",
            Name = "Smith",
        });
        EmployeeDetails.Add(new TeamDetails
        {
            Id = "01-02",
            Name = "Johnson",
        });
        EmployeeDetails.Add(new TeamDetails
        {
            Id = "01-03",
            Name = "Anderson"
        });

        List<TeamDetails> EmployeeDetails1 = new List<TeamDetails>();

        Team.Add(new TeamDetails
        {
            Id = "02",
            Name = "Windows Team",
            Children = EmployeeDetails1,
        });
        EmployeeDetails1.Add(new TeamDetails
        {
            Id = "02-01",
            Name = "Clark"
        });
        EmployeeDetails1.Add(new TeamDetails
        {
            Id = "02-02",
            Name = "Wright"
        });

        List<TeamDetails> EmployeeDetails2 = new List<TeamDetails>();

        Team.Add(new TeamDetails
        {
            Id = "03",
            Name = "Web Team",
            Children = EmployeeDetails2,
        });
        EmployeeDetails2.Add(new TeamDetails
        {
            Id = "03-01",
            Name = "Joshua"
        });
        EmployeeDetails2.Add(new TeamDetails
        {
            Id = "03-02",
            Name = "Matthew"
        });
    }
}

Multiple-node drag and drop

To drag and drop more than one node, enable the AllowMultiSelection property along with the AllowDragAndDrop property. To perform multi-selection, press and hold CTRL key and click the desired nodes. To select range of nodes, press and hold the SHIFT key and click the nodes.

In the following sample, the AllowMultiSelection property is enabled along with the AllowDragAndDrop property.

@using Syncfusion.Blazor.Navigations
<SfTreeView TValue="TeamDetails" AllowDragAndDrop="true" AllowMultiSelection="true">
    <TreeViewFieldsSettings TValue="TeamDetails" Id="Id" Text="Name" Selected="Selected" Child="Children" DataSource="@Team" Expanded="Expanded"></TreeViewFieldsSettings>
</SfTreeView>

@code{
    public class TeamDetails
    {
        public string Id { get; set; }
        public string Name { get; set; }
        public bool Expanded { get; set; }
        public bool Selected { get; set; }
        public List<TeamDetails> Children;
    }

    List<TeamDetails> Team = new List<TeamDetails>();

    protected override void OnInitialized()
    {
        base.OnInitialized();
        List<TeamDetails> EmployeeDetails = new List<TeamDetails>();
        Team.Add(new TeamDetails
        {
            Id = "01",
            Name = "ASP.NET MVC Team",
            Expanded = true,
            Children = EmployeeDetails,
        });
        EmployeeDetails.Add(new TeamDetails
        {
            Id = "01-01",
            Name = "Smith",
            Selected = true
        });
        EmployeeDetails.Add(new TeamDetails
        {
            Id = "01-02",
            Name = "Johnson",
            Selected = true
        });
        EmployeeDetails.Add(new TeamDetails
        {
            Id = "01-03",
            Name = "Anderson"
        });

        List<TeamDetails> EmployeeDetails1 = new List<TeamDetails>();

        Team.Add(new TeamDetails
        {
            Id = "02",
            Name = "Windows Team",
            Children = EmployeeDetails1,
        });
        EmployeeDetails1.Add(new TeamDetails
        {
            Id = "02-01",
            Name = "Clark"
        });
        EmployeeDetails1.Add(new TeamDetails
        {
            Id = "02-02",
            Name = "Wright"
        });

        List<TeamDetails> EmployeeDetails2 = new List<TeamDetails>();

        Team.Add(new TeamDetails
        {
            Id = "03",
            Name = "Web Team",
            Children = EmployeeDetails2,
        });
        EmployeeDetails2.Add(new TeamDetails
        {
            Id = "03-01",
            Name = "Joshua"
        });
        EmployeeDetails2.Add(new TeamDetails
        {
            Id = "03-02",
            Name = "Matthew"
        });
    }
}