Blazorise TreeView component

The TreeView component is a graphical control element that presents a hierarchical view of information.

The TreeView component is a powerful and flexible way to display hierarchical data in a tree-like structure. It allows users to navigate through the tree and perform actions on the nodes, such as expanding or collapsing them, selecting them, or performing other operations.

Features

Display hierarchical data in a tree structure.
Expand or collapse nodes.
Select single or multiple nodes (depending on the selection mode).
Allow Node Items to be disabled for selection.
Customize the appearance of the nodes using templates.
Perform actions on the nodes, such as deleting them or performing some other operation.

Installation

To install the Blazorise TreeView component, run the following command in the Package Manager Console:

Install-Package Blazorise.TreeView

Alternatively, you can install the package using the .NET Core CLI:

dotnet add package Blazorise.TreeView

Configuration

Once the package is installed, you need to configure your Blazor project to use the TreeView component.

In your main _Imports.razor add:

@using Blazorise.TreeView

Static files

Include CSS link into your index.html or _Layout.cshtml / _Host.cshtml file, depending if you’re using a Blazor WebAssembly or Blazor Server side project.

<link href="_content/Blazorise.TreeView/blazorise.treeview.css" rel="stylesheet" />

Basic example

A basic TreeView that aims to reproduce standard tree-view behavior.

Item 1

Item 2

Item 3

<TreeView Nodes="Items"
          GetChildNodes="@(item => item.Children)"
          HasChildNodes="@(item => item.Children?.Any() == true)"
          @bind-SelectedNode="selectedNode"
          @bind-ExpandedNodes="expandedNodes">
    <NodeContent>
        <Icon Name="IconName.Folder" />
        @context.Text
    </NodeContent>
</TreeView>

@code{
    public class Item
    {
        public string Text { get; set; }
        public IEnumerable<Item> Children { get; set; }
    }

    IEnumerable<Item> Items = new[]
    {
        new Item { Text = "Item 1" },
        new Item
        {
            Text = "Item 2",
            Children = new []
            {
                new Item { Text = "Item 2.1" },
                new Item
                {
                    Text = "Item 2.2",
                    Children = new []
                    {
                        new Item { Text = "Item 2.2.1" },
                        new Item { Text = "Item 2.2.2" },
                        new Item { Text = "Item 2.2.3" },
                        new Item { Text = "Item 2.2.4" }
                    }
                },
                new Item { Text = "Item 2.3" },
                new Item { Text = "Item 2.4" }
            }
        },
        new Item { Text = "Item 3" },
    };

    IList<Item> expandedNodes = new List<Item>();
    Item selectedNode;
}

Expanding and Collapsing Nodes

By default, all nodes are collapsed except for the root node(s). To expand a node, click on the triangle icon next to its label. To collapse a node, click on the triangle icon again. You can also programmatically expand or collapse nodes using the ExpandAll() and CollapseAll() property of the TreeView class.

Item 1

Item 2

Item 3

<Button Color="Color.Primary" Clicked="@(()=>treeViewRef.ExpandAll())">Expand all</Button>
<Button Color="Color.Secondary" Clicked="@(()=>treeViewRef.CollapseAll())">Collapse all</Button>

<TreeView @ref="@treeViewRef" Nodes="Items" GetChildNodes="@(item => item.Children)" HasChildNodes="@(item => item.Children?.Any() == true)">
    <NodeContent>
        <Icon Name="IconName.Folder" />
        @context.Text
    </NodeContent>
</TreeView>

@code {
    TreeView<Item> treeViewRef;

    public class Item
    {
        public string Text { get; set; }
        public IEnumerable<Item> Children { get; set; }
    }

    IEnumerable<Item> Items = new[]
    {
        new Item { Text = "Item 1" },
        new Item
        {
            Text = "Item 2",
            Children = new []
            {
                new Item { Text = "Item 2.1" },
                new Item
                {
                    Text = "Item 2.2",
                    Children = new []
                    {
                        new Item { Text = "Item 2.2.1" },
                        new Item { Text = "Item 2.2.2" },
                        new Item { Text = "Item 2.2.3" },
                        new Item { Text = "Item 2.2.4" }
                    }
                },
                new Item { Text = "Item 2.3" },
                new Item { Text = "Item 2.4" }
            }
        },
        new Item { Text = "Item 3" },
    };
}

Multiple selection

The TreeView component multiple selection mode, allows users to select multiple nodes at the same time. To enable this mode, set the SelectionMode property to Multiple. When this mode is enabled, each node in the TreeView will display a checkbox next to its label. Users can then select or deselect nodes by clicking on the checkboxes.

The selected nodes can be accessed through the SelectedNodes property, which returns a list of the selected nodes. You can also use the SelectedNodesChanged event to be notified when the selection changes.

Item 1

Item 2

Item 3

<TreeView Nodes="Items"
          GetChildNodes="@(item => item.Children)"
          HasChildNodes="@(item => item.Children?.Any() == true)"
          SelectionMode="TreeViewSelectionMode.Multiple"
          @bind-SelectedNodes="selectedNodes">
    <NodeContent>
        <Icon Name="IconName.Folder" />
        @context.Text
    </NodeContent>
</TreeView>

@code {
    public class Item
    {
        public string Text { get; set; }
        public IEnumerable<Item> Children { get; set; }
    }

    IEnumerable<Item> Items = new[]
    {
        new Item { Text = "Item 1" },
        new Item
        {
            Text = "Item 2",
            Children = new []
            {
                new Item { Text = "Item 2.1" },
                new Item
                {
                    Text = "Item 2.2",
                    Children = new []
                    {
                        new Item { Text = "Item 2.2.1" },
                        new Item { Text = "Item 2.2.2" },
                        new Item { Text = "Item 2.2.3" },
                        new Item { Text = "Item 2.2.4" }
                    }
                },
                new Item { Text = "Item 2.3" },
                new Item { Text = "Item 2.4" }
            }
        },
        new Item { Text = "Item 3" },
    };

    IList<Item> selectedNodes = new List<Item>();
}

Observable Lists

The Observable Lists feature in Blazorise TreeView component enables automatic updates and synchronization of the TreeView data with the underlying data source. This is achieved through the implementation of an observable pattern where the TreeView component listens to changes in the data source, and updates its visual representation accordingly.

When using Observable Lists in the Blazorise TreeView component, any modifications to the underlying data source, such as adding, removing, or updating nodes, will automatically trigger the necessary updates in the TreeView component. This ensures that the TreeView always reflects the most up-to-date state of the data.

It is of note that the Nodes parameter is a one way bound collection and as such, if you want to add and remove items, it is recommended that it is used as an ObservableCollection in order to keep the TreeView properly synced across refreshes.

Item 1

Item 2

Item 3

@using System.Collections.ObjectModel;
@using Blazorise.Extensions

<Row>
    <Column>
        <Button Clicked="@OnAddNodeClick" Color="Color.Primary">Add node</Button>
        <Button Clicked="@OnRemoveNodeClick" Color="Color.Danger">Remove node</Button>
    </Column>
    <Column>
        <TreeView Nodes="Items"
                  GetChildNodes="@(item => item.Children)"
                  HasChildNodes="@(item => item.Children?.Any() == true)"
                  @bind-SelectedNode="selectedNode"
                  @bind-ExpandedNodes="expandedNodes">
            <NodeContent>
                <Icon Name="IconName.Folder" />
                @context.Text
            </NodeContent>
        </TreeView>
    </Column>
</Row>

@code {
    private Task OnAddNodeClick()
    {
        Items.Add( new Item { Text = $"Item {Items.Count + 1}" } );

        return Task.CompletedTask;
    }

    private async Task OnRemoveNodeClick()
    {
        if ( selectedNode is null )
            return;

        await RemoveItem( selectedNode );
    }

    public Task RemoveItem( Item item )
    {
        SearchTryRemoveItem( Items, item );
        return Task.CompletedTask;
    }

    private void SearchTryRemoveItem( ObservableCollection<Item> rows, Item item )
    {
        if ( rows.IsNullOrEmpty() )
            return;

        var nodeToRemove = rows.FirstOrDefault( x => x.Equals( item ) );

        if ( nodeToRemove is not null )
        {
            rows.Remove( nodeToRemove );
        }
        else
        {
            foreach ( var row in rows )
            {
                SearchTryRemoveItem( row.Children, item );
            }
        }
    }

    public class Item
    {
        public string Text { get; set; }
        public ObservableCollection<Item> Children { get; set; }
    }

    ObservableCollection<Item> Items = new()
    {
        new Item { Text = "Item 1" },
        new Item
        {
            Text = "Item 2",
            Children = new ObservableCollection<Item>()
            {
                new Item { Text = "Item 2.1" },
                new Item
                {
                    Text = "Item 2.2",
                    Children = new ObservableCollection<Item>()
                    {
                        new Item { Text = "Item 2.2.1" },
                        new Item { Text = "Item 2.2.2" },
                        new Item { Text = "Item 2.2.3" },
                        new Item { Text = "Item 2.2.4" }
                    }
                },
                new Item { Text = "Item 2.3" },
                new Item { Text = "Item 2.4" }
            }
        },
        new Item { Text = "Item 3" },
    };

    IList<Item> expandedNodes = new List<Item>();
    Item selectedNode;
}

Node Context Menu

To integrate the context menu with the TreeView, you need to:

Use the TreeView NodeContextMenu event to get the current node and show the menu.
Use the context menu's MouseEventArgs parameter to handle the desired operation.

In this example, the context menu is used to show the menu items, put an item in edit mode and delete items.

Item 1

Item 2

Item 2.1

Item 2.2

Item 2.2.1

Item 2.2.2

Item 2.2.3

Item 2.2.4

Item 2.3

Item 2.4

Item 3

@using System.Drawing

<TreeView TNode="Item"
          Nodes="Items"
          GetChildNodes="@(item => item.Children)"
          HasChildNodes="@(item => item.Children?.Any() == true)"
          AutoExpandAll
          @bind-SelectedNode="selectedNode"
          @bind-ExpandedNodes="expandedNodes"
          NodeContextMenu="@OnNodeContextMenu"
          NodeContextMenuPreventDefault>
    <NodeContent>
        <Icon Name="IconName.Folder" />
        @context.Text
    </NodeContent>
</TreeView>

@if ( showContextMenu )
{
    <Div Position="Position.Fixed" Background="Background.Danger" Style="@($"left:{contextMenuPosX}px; top:{contextMenuPosY}px;")">
        <ListGroup>
            <ListGroupItem>
                <Strong>Node: @contextMenuNode?.Text</Strong>
            </ListGroupItem>
            <ListGroupItem Clicked="@(()=>OnContextItemEditClicked(contextMenuNode))" Style="cursor: pointer;">
                <Icon Name="IconName.Edit" TextColor="TextColor.Secondary" /> Edit
            </ListGroupItem>
            <ListGroupItem Clicked="@(()=>OnContextItemDeleteClicked(contextMenuNode))" Style="cursor: pointer;">
                <Icon Name="IconName.Delete" TextColor="TextColor.Danger" /> Delete
            </ListGroupItem>
        </ListGroup>
    </Div>
}

@code {
    public class Item
    {
        public string Text { get; set; }
        public IEnumerable<Item> Children { get; set; }
    }

    IEnumerable<Item> Items = new[]
    {
        new Item { Text = "Item 1" },
        new Item
        {
            Text = "Item 2",
            Children = new []
            {
                new Item { Text = "Item 2.1" },
                new Item
                {
                    Text = "Item 2.2",
                    Children = new []
                    {
                        new Item { Text = "Item 2.2.1" },
                        new Item { Text = "Item 2.2.2" },
                        new Item { Text = "Item 2.2.3" },
                        new Item { Text = "Item 2.2.4" }
                    }
                },
                new Item { Text = "Item 2.3" },
                new Item { Text = "Item 2.4" }
            }
        },
        new Item { Text = "Item 3" },
    };

    IList<Item> expandedNodes = new List<Item>();
    Item selectedNode;

    bool showContextMenu = false;
    double contextMenuPosX;
    double contextMenuPosY;
    Item contextMenuNode;

    protected Task OnNodeContextMenu( TreeViewNodeMouseEventArgs<Item> eventArgs )
    {
        showContextMenu = true;
        contextMenuNode = eventArgs.Node;
        contextMenuPosX = eventArgs.MouseEventArgs.ClientX;
        contextMenuPosY = eventArgs.MouseEventArgs.ClientY;

        return Task.CompletedTask;
    }

    protected Task OnContextItemEditClicked( Item item )
    {
        showContextMenu = false;

        return Task.CompletedTask;
    }

    protected Task OnContextItemDeleteClicked( Item item )
    {
        showContextMenu = false;

        return Task.CompletedTask;
    }
}

API

Attributes

Name	Description	Type	Default
`Nodes`	Collection of child TreeView items (child nodes). If null/empty then this node won’t expand.	`IEnumerable<TNode>`
`NodeContent`	Template to display content for the node.	`RenderFragment<TNode>`
`SelectionMode`	Defines the selection mode of the TreeView.	`TreeViewSelectionMode`	`Single`
`SelectedNode`	The currently selected TreeView item/node.	`TNode`
`SelectedNodeChanged`	Occurs when the selected TreeView node has changed.	`EventCallback<TNode>`
`SelectedNodes`	The currently selected TreeView items/nodes.	`IList<TNode>`
`SelectedNodesChanged`	Occurs when the selected TreeView nodes are changed.	`EventCallback<IList<TNode>>`
`AutoExpandAll`	Defines if the treenode should be automatically expanded. Note that it can happen only once when the tree is first loaded.	`bool`	`false`
`ExpandedNodes`	List of currently expanded TreeView items (child nodes).	`List<TNode>`
`ExpandedNodeChanged`	Occurs when the collection of expanded nodes has changed.	`EventCallback<TNode>`
`GetChildNodes`	Expression that allows the child nodes to be identified for a particular node.	`Func<TNode, IEnumerable<TNode>>`
`HasChildNodes`	Expression that indicates whether the current node has any children nodes?	`Func<TNode, bool>`	`(node) => false`
`IsDisabled`	Expression that indicates whether the current node should be disabled from selection	`Func<TNode, bool>`	`(node) => false`
`GetChildNodesAsync`	Asynchronous expression that allows the child nodes to be identified for a particular node.	`Func<TNode, Task<IEnumerable<TNode>>>`
`HasChildNodesAsync`	Asynchronous expression that indicates whether the current node has any children nodes?	`Func<TNode, Task<bool>>`	`null`
`ExpandIconName`	Defines the name of the treenode expand icon.	`IconName`	`ChevronRight`
`ExpandIconStyle`	Defines the style of the treenode expand icon.	`IconStyle?`	`null`
`ExpandIconSize`	Defines the size of the treenode expand icon.	`IconSize?`	`null`
`CollapseIconName`	Defines the name of the treenode collapse icon.	`IconName`	`ChevronRight`
`CollapseIconStyle`	Defines the style of the treenode collapse icon.	`IconStyle?`	`null`
`CollapseIconSize`	Defines the size of the treenode collapse icon.	`IconSize?`	`null`
`NodeContextMenu`	The event is fired when the node is right clicked to show the context menu.	`EventCallback<TreeViewNodeMouseEventArgs<TNode>>`
`NodeContextMenuPreventDefault`	Used to prevent the default action for a NodeContextMenu event.	`bool`	`false`

Methods

Name	Description	Return	Parameters
`ExpandAll()`	Expands all the collapsed TreeView nodes.	`Task`
`CollapseAll()`	Collapses all the expanded TreeView nodes.	`Task`
`ToggleCheckNode()`	Toggles the checked state of the node when in multiple selection mode.	`Task`	`TNode node`
`SelectNode()`	Selects the node when in single selection mode.	`void`	`TNode node`
`RemoveNode()`	Attempts to find and remove an existing node from the TreeView.	`Task`	`TNode node`
`Reload()`	Triggers the reload of the TreeView Nodes.	`Task`

Blazorise TreeView component

Features

Installation

Configuration

Static files

Basic example

Expanding and Collapsing Nodes

Multiple selection

Observable Lists

Node Context Menu

API

Attributes

Methods

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