Angular TreeView Properties

The value of this option will be passed to the accesskey attribute of the HTML element that underlies the widget.

This option is used when the widget is displayed on a platform whose guidelines include the active state change for widgets.

This function is called at the beginning of the widget's lifetime and each time a user expands a node whose child nodes have not been loaded yet. It allows you to load the entire tree in portions: load root nodes first (when the function's parentNode parameter is null) and the child nodes of each expanded node later.

The following code shows how to use this function with a remote service:

$(function() {
    $("#treeViewContainer").dxTreeView({
        dataStructure: "plain",
        rootValue: 0, 
        createChildren: function (parentNode) {
            var d = $.Deferred();
            $.get("http://url/to/the/service", {
                    // Here, 0 is the "rootValue" option's value.
                    parentId: parentNode ? JSON.stringify(parentNode.key) : "0" 
                })
                .done(function (result) {
                    d.resolve(result);
                });
            return d.promise();
        }
    });
});

<dx-tree-view
    [rootValue]="0"
    dataStructure="plain"
    [createChildren]="createChildren">
</dx-tree-view>

import { ..., Inject } from "@angular/core";
import { HttpClient, HttpClientModule, HttpParams } from "@angular/common/http";
import "rxjs/add/operator/toPromise";
import { DxTreeViewModule } from "devextreme-angular";
// ...
export class AppComponent {
    constructor(@Inject(HttpClient) httpClient: HttpClient) { }
    createChildren = (parentNode) => {
        let params: HttpParams = new HttpParams()
            // Here, 0 is the "rootValue" option's value.
            .set("parentId", parentNode ? JSON.stringify(parentNode.key) : "0"); 
        return httpClient.get("http://url/to/the/service", {
                params: params
            })
            .toPromise();
    }
}
@NgModule({
    imports: [
        // ...
        DxTreeViewModule,
        HttpClientModule 
    ],
    // ...
})

View Demo

See Also

• Enhance Performance on Large Datasets
• TreeView - Use Plain Data

If you use DevExtreme ASP.NET MVC Controls, refer to the Data Binding article.

The TreeView works with object collections that can have a plain or hierarchical structure. Depending on the structure, the objects should provide different data fields. Specify the dataStructure option to notify the TreeView of the used structure and refer to the option's description for information on the required fields.

Depending on your data source, bind the TreeView to data as follows.

• Data Array
  Assign the array to the dataSource option.

• Read-Only Data in JSON Format
  Set the dataSource option to the URL of a JSON file or service that returns JSON data.

• OData
  Implement an ODataStore.

• Web API, PHP, MongoDB
  Use one of the following extensions to enable the server to process data according to the protocol DevExtreme widgets use:

  • DevExtreme.AspNet.Data
  • DevExtreme-PHP-Data
  • devextreme-query-mongodb

  Then, use the createStore method to configure access to the server on the client as shown below. This method is part of DevExtreme.AspNet.Data.

  jQuery

  JavaScript

  $(function() {
      let serviceUrl = "https://url/to/my/service";
      $("#treeViewContainer").dxTreeView({
          // ...
          dataSource: DevExpress.data.AspNet.createStore({
              key: "ID",
              loadUrl: serviceUrl + "/GetAction",
              insertUrl: serviceUrl + "/InsertAction",
              updateUrl: serviceUrl + "/UpdateAction",
              deleteUrl: serviceUrl + "/DeleteAction"
          })
      })
  });

  Angular

  app.component.ts

  app.component.html

  app.module.ts

  import { Component } from '@angular/core';
  import CustomStore from 'devextreme/data/custom_store';
  import { createStore } from 'devextreme-aspnet-data-nojquery';
  
  @Component({
      selector: 'app-root',
      templateUrl: './app.component.html',
      styleUrls: ['./app.component.css']
  })
  export class AppComponent {
      store: CustomStore;
      constructor() {
          let serviceUrl = "https://url/to/my/service";
          this.store = createStore({
              key: "ID",
              loadUrl: serviceUrl + "/GetAction",
              insertUrl: serviceUrl + "/InsertAction",
              updateUrl: serviceUrl + "/UpdateAction",
              deleteUrl: serviceUrl + "/DeleteAction"
          })
      }
  }

  <dx-tree-view ...
      [dataSource]="store">
  </dx-tree-view>

  import { BrowserModule } from '@angular/platform-browser';
  import { NgModule } from '@angular/core';
  import { AppComponent } from './app.component';
  
  import { DxTreeViewModule } from 'devextreme-angular';
  
  @NgModule({
      declarations: [
          AppComponent
      ],
      imports: [
          BrowserModule,
          DxTreeViewModule
      ],
      providers: [],
      bootstrap: [AppComponent]
  })
  export class AppModule { }

  Vue

  App.vue

  <template> 
      <dx-tree-view ...
          :data-source="store" />
  </template>
  
  <script>
  import 'devextreme/dist/css/dx.common.css';
  import 'devextreme/dist/css/dx.light.css';
  
  import CustomStore from 'devextreme/data/custom_store';
  import { createStore } from 'devextreme-aspnet-data-nojquery';
  import { DxTreeView } from 'devextreme-vue/tree-view';
  
  export default {
      components: {
          DxTreeView
      },
      data() {
          const serviceUrl = "https://url/to/my/service";
          const store = createStore({
              key: "ID",
              loadUrl: serviceUrl + "/GetAction",
              insertUrl: serviceUrl + "/InsertAction",
              updateUrl: serviceUrl + "/UpdateAction",
              deleteUrl: serviceUrl + "/DeleteAction"
          });
          return {
              store
          }
      }
  }
  </script>

  React

  App.js

  import React from 'react';
  import 'devextreme/dist/css/dx.common.css';
  import 'devextreme/dist/css/dx.light.css';
  
  import CustomStore from 'devextreme/data/custom_store';
  import { createStore } from 'devextreme-aspnet-data-nojquery';
  import TreeView from 'devextreme-react/tree-view';
  
  const serviceUrl = "https://url/to/my/service";
  const store = createStore({
      key: "ID",
      loadUrl: serviceUrl + "/GetAction",
      insertUrl: serviceUrl + "/InsertAction",
      updateUrl: serviceUrl + "/UpdateAction",
      deleteUrl: serviceUrl + "/DeleteAction"
  });
  
  class App extends React.Component {
      render() {
          return (
              <TreeView ...
                  dataSource={store} />
          );
      }
  }
  export default App;

• Any other data source
  Implement a CustomStore.

Regardless of the data source on the input, the TreeView always wraps it in the DataSource object. This object allows you to sort, filter, group, and otherwise shape data. To get its instance, call the getDataSource() method.

See Also

• Enhance Performance on Large Datasets

The widget expects that data has a hierarchical structure where each data item contains a text, a unique id, and an items array if the data item nests other data items:

var hierarchicalData = [{
    id: '1',
    text: 'Fruits',
    items: [
        { id: '1_1', text: 'Apples' },
        { id: '1_2', text: 'Oranges' }
    ]
}, {
    id: '2',
    text: 'Vegetables',
    items: [
        { id: '2_1', text: 'Cucumbers' },
        { id: '2_2', text: 'Tomatoes' }
    ]
}];

View Demo

If data has a plain structure, set the dataStructure option to "plain". In this case, each data item should have a text, a unique id, and a parentId. For root items, parentId should be equal to 0 or undefined:

var plainData = [
    { id: '1', text: 'Fruits' },     // A root item
    { id: '1_1', text: 'Apples', parentId: '1' },
    { id: '1_2', text: 'Oranges', parentId: '1' },
    { id: '2', text: 'Vegetables' }, // Also a root item
    { id: '2_1', text: 'Cucumbers', parentId: '2' },
    { id: '2_2', text: 'Tomatoes', parentId: '2' }
];

id, text, items, and parentId are conventional field names defined in the Default Item Template. To use other names, change the keyExpr, displayExpr, itemsExpr, and parentIdExpr options, respectively. You can also specify the rootValue option to change the parentId value that root items should have.

View Demo

Use the TreeViewDataStructure enum to specify this option when the widget is used as an ASP.NET MVC Control. This enum accepts the following values: Plain and Tree.

See Also

• TreeView - Use Hierarchical Data
• TreeView - Use Plain Data

Set this option to the name of a data field that provides displayed values...

displayExpr: "name"

... or to a function that combines the values of several data fields to create the displayed value:

displayExpr: function(item) {
    // "item" can be null
    return item && 'ID: ' + item.id + ', Name: ' + item.name;
}

View Demo

See Also

• Use Hierarchical Data
• Use Plain Data

See Also

• expandEvent
• Expand and Collapse Nodes

Use the TreeViewExpandEvent enum to specify this option when the widget is used as an ASP.NET MVC Control. This enum accepts the following values: DblClick and Click.

This option accepts a value of one of the following types:

• Number
  The height in pixels.

• String
  A CSS-accepted measurement of height. For example, "55px", "80%", "auto", "inherit".

• Function
  A function returning either of the above. For example:

  JavaScript

  height: function() {
      return window.innerHeight / 1.5;
  }

You can use the dataSource option instead. Unlike the items option, the dataSource option can take on the DataSource configuration object as well as a simple array.

To display widget items, a default template can be used. This template is based on the data source fields that are listed in the Default Item Template section of the widget's API.

See Also

• Customize Node Appearance
• Custom Templates

See Also

• Specify data using dataSource option
• Specify data using items option

See Also

• Get a Widget Instance in Angular | AngularJS | Knockout | Vue | React

See Also

-Expand and Collapse Nodes - Events

See Also

• Expand and Collapse Nodes - Events

This function is executed under one of the following conditions:

• The selectByClick option is set to true;
• The showCheckBoxesMode option is not "none";
• One of the following methods is called: selectAll(), unselectAll(), selectItem(), unselectItem().

View Demo

See Also

• Select Nodes - Events

See Also

• onSelectionChanged
• Select Nodes

This function is executed under one of the following conditions:

• The selectByClick option is set to true;
• The showCheckBoxesMode option is not "none";
• One of the following methods is called: selectAll(), unselectAll(), selectItem(), unselectItem().

This option is used if the dataStructure option is set to "plain".

View Demo

When this option is set to true, the widget text flows from right to left, and the layout of elements is reversed. To switch the entire application/site to the right-to-left representation, assign true to the rtlEnabled field of the object passed to the DevExpress.config(config) method.

DevExpress.config({
    rtlEnabled: true
});

See Also

• Right-to-Left Support Demo: DataGrid | Navigation Widgets | Editors

Use the ScrollDirection enum to specify this option when the widget is used as an ASP.NET MVC Control. This enum accepts the following values: Vertical, Horizontal, and Both.

See the TextBox Configuration for options you can specify in this object.

View Demo

See Also

• TreeView - Searching

If you need to search several fields, assign an array of field names to this option.

searchExpr: ["firstName", "lastName"]

Use the CollectionSearchMode enum to specify this option when the widget is used as an ASP.NET MVC Control. This enum accepts the following values: Contains, StartsWith, and Equals.

See Also

• Search Nodes

See Also

• Select Nodes - User Interaction

Use the NavSelectionMode enum to specify this option when the widget is used as an ASP.NET MVC Control. This enum accepts the following values: Single and Multiple.

If this option is enabled, the widget selects (unselects) all child nodes if a user selects (unselects) the parent node.

The option accepts the following values.

• "none"
  The widget does not display check boxes.

• "normal"
  The widget displays a check box for each item.

• "selectAll"
  The widget displays a check box for each item and the "select all" check box at the top of the widget.

Use the TreeViewCheckBoxMode enum to specify this option when the widget is used as an ASP.NET MVC Control. This enum accepts the following values: None, Normal, and SelectAll.

View Demo

See Also

• Select Nodes - User Interaction

The value of this option will be passed to the tabindex attribute of the HTML element that underlies the widget.

If the option is set to true, the widget initially loads only root items. Child items are loaded when their parent is being expanded.

Use this option to improve the widget performance when working with a huge data source.

View Demo

See Also

• Enhance Performance on Large Datasets
• createChildren - allows you to load nodes manually.

This option accepts a value of one of the following types:

• Number
  The width in pixels.

• String
  A CSS-accepted measurement of width. For example, "55px", "80%", "auto", "inherit".

• Function
  A function returning either of the above. For example:

  JavaScript

  width: function() {
      return window.innerWidth / 1.5;
  }