Load Data on Demand
The TreeList can load a remote dataset dynamically as a user expands nodes. The dataset must have a plain structure.
This feature requires client- and server-side configurations. To configure the client-side part, do the following:
-
Send an expanded node's ID to the server
For this, implement the CustomStore's load function. In this demo, we do it in the dataSource configuration object. -
Delegate filtering to the server
Set the remoteOperations.filtering property to true. -
Specify the data field that defines whether the node has children
Use the hasItemsExpr property to set this data field.
Server-side implementation is available in the ASP.NET Core and ASP.NET MVC versions of this demo under the TreeListDataController.cs tab.
NOTE
This demo uses a simple data bind technique that is useful for data display purposes only. When a user clicks a node, TreeList receives a JSON object from the server, which is based on the parentIds property value. This technique does not support the built-in data process operations in TreeList on the server.
If your project needs to process data, do one of the following instead:
- Implement a custom data source. See the Custom Data Source demo.
- Use the DevExtreme.AspNet.Data extension as shown in the Web API Service demo.
Feel free to share demo-related thoughts here.
If you have technical questions, please create a support ticket in the DevExpress Support Center.
If you have technical questions, please create a support ticket in the DevExpress Support Center.
Thank you!
We appreciate your feedback.
We appreciate your feedback.
<dx-tree-list
id="treelist"
[dataSource]="dataSource"
[showBorders]="true"
[remoteOperations]="{ filtering: true }"
keyExpr="id"
parentIdExpr="parentId"
hasItemsExpr="hasItems"
rootValue=""
>
<dxi-column dataField="name"></dxi-column>
<dxi-column
dataField="size"
[width]="100"
[customizeText]="customizeSizeText"
></dxi-column>
<dxi-column
dataField="createdDate"
dataType="date"
[width]="150"
></dxi-column>
<dxi-column
dataField="modifiedDate"
dataType="date"
[width]="150"
></dxi-column>
</dx-tree-list>
import { NgModule, Component, enableProdMode } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
import { HttpClient, HttpClientModule, HttpParams } from '@angular/common/http';
import { lastValueFrom } from 'rxjs';
import { DxTreeListModule } from 'devextreme-angular';
if (!/localhost/.test(document.location.host)) {
enableProdMode();
}
@Component({
selector: 'demo-app',
templateUrl: 'app/app.component.html',
styleUrls: ['app/app.component.css'],
})
export class AppComponent {
dataSource: any;
constructor(http: HttpClient) {
this.dataSource = {
load(loadOptions) {
let params = new HttpParams();
if (loadOptions.parentIds) {
loadOptions.parentIds.forEach((id) => {
params = params.append('parentIds', id);
});
}
return lastValueFrom(
http.get('https://js.devexpress.com/Demos/Mvc/api/treeListData', { params }),
);
},
};
}
customizeSizeText(e) {
if (e.value !== null) {
return `${Math.ceil(e.value / 1024)} KB`;
}
}
}
@NgModule({
imports: [
BrowserModule,
DxTreeListModule,
HttpClientModule,
],
declarations: [AppComponent],
bootstrap: [AppComponent],
})
export class AppModule { }
platformBrowserDynamic().bootstrapModule(AppModule);
::ng-deep #treelist {
max-height: 440px;
}
// In real applications, you should not transpile code in the browser.
// You can see how to create your own application with Angular and DevExtreme here:
// https://js.devexpress.com/Documentation/Guide/Angular_Components/Getting_Started/Create_a_DevExtreme_Application/
window.config = {
transpiler: 'ts',
typescriptOptions: {
module: 'system',
emitDecoratorMetadata: true,
experimentalDecorators: true,
},
meta: {
'typescript': {
'exports': 'ts',
},
'devextreme/localization.js': {
'esModule': true,
},
},
paths: {
'npm:': 'https://unpkg.com/',
},
map: {
'ts': 'npm:plugin-typescript@4.2.4/lib/plugin.js',
'typescript': 'npm:typescript@4.2.4/lib/typescript.js',
'@angular/core': 'npm:@angular/core@12.2.16',
'@angular/platform-browser': 'npm:@angular/platform-browser@12.2.16',
'@angular/platform-browser-dynamic': 'npm:@angular/platform-browser-dynamic@12.2.16',
'@angular/forms': 'npm:@angular/forms@12.2.16',
'@angular/common': 'npm:@angular/common@12.2.16',
'@angular/compiler': 'npm:@angular/compiler@12.2.16',
'tslib': 'npm:tslib@2.3.1/tslib.js',
'rxjs': 'npm:rxjs@7.5.3/dist/bundles/rxjs.umd.js',
'rxjs/operators': 'npm:rxjs@7.5.3/dist/cjs/operators/index.js',
'rrule': 'npm:rrule@2.6.4/dist/es5/rrule.js',
'luxon': 'npm:luxon@1.28.0/build/global/luxon.min.js',
'es6-object-assign': 'npm:es6-object-assign@1.1.0',
'devextreme': 'npm:devextreme@22.1.4/cjs',
'devextreme/bundles/dx.all': 'npm:devextreme@22.1.4/bundles/dx.all.js',
'jszip': 'npm:jszip@3.7.1/dist/jszip.min.js',
'devextreme-quill': 'npm:devextreme-quill@1.5.16/dist/dx-quill.min.js',
'devexpress-diagram': 'npm:devexpress-diagram@2.1.63',
'devexpress-gantt': 'npm:devexpress-gantt@4.1.32',
'devextreme-angular': 'npm:devextreme-angular@22.1.4',
'@devextreme/runtime': 'npm:@devextreme/runtime@3.0.7',
'inferno': 'npm:inferno@7.4.4/dist/inferno.min.js',
'inferno-compat': 'npm:inferno-compat@7.4.11/dist/inferno-compat.min.js',
'inferno-create-element': 'npm:inferno-create-element@7.4.11/dist/inferno-create-element.min.js',
'inferno-dom': 'npm:inferno-dom/dist/inferno-dom.min.js',
'inferno-hydrate': 'npm:inferno-hydrate@7.4.11/dist/inferno-hydrate.min.js',
'inferno-clone-vnode': 'npm:inferno-clone-vnode@7.4.11/dist/inferno-clone-vnode.min.js',
'inferno-create-class': 'npm:inferno-create-class@7.4.11/dist/inferno-create-class.min.js',
'inferno-extras': 'npm:inferno-extras@7.4.11/dist/inferno-extras.min.js',
},
packages: {
'app': {
main: './app.component.ts',
defaultExtension: 'ts',
},
'devextreme': {
defaultExtension: 'js',
},
'devextreme/events/utils': {
main: 'index',
},
'devextreme/events': {
main: 'index',
},
'es6-object-assign': {
main: './index.js',
defaultExtension: 'js',
},
'rxjs': {
defaultExtension: 'js',
},
'rxjs/operators': {
defaultExtension: 'js',
},
},
packageConfigPaths: [
'npm:@devextreme/*/package.json',
'npm:@devextreme/runtime@3.0.7/inferno/package.json',
'npm:@angular/*/package.json',
'npm:@angular/common@12.2.16/*/package.json',
'npm:rxjs@7.5.3/package.json',
'npm:rxjs@7.5.3/operators/package.json',
'npm:devextreme-angular@22.1.4/*/package.json',
'npm:devextreme-angular@22.1.4/ui/*/package.json',
'npm:devextreme-angular@22.1.4/package.json',
'npm:devexpress-diagram@2.1.63/package.json',
'npm:devexpress-gantt@4.1.32/package.json',
],
};
System.config(window.config);
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>DevExtreme Demo</title>
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0" />
<link rel="stylesheet" type="text/css" href="https://cdn3.devexpress.com/jslib/22.1.4/css/dx.common.css" />
<link rel="stylesheet" type="text/css" href="https://cdn3.devexpress.com/jslib/22.1.4/css/dx.light.css" />
<script src="https://unpkg.com/core-js@2.4.1/client/shim.min.js"></script>
<script src="https://unpkg.com/zone.js@0.11.4/dist/zone.js"></script>
<script src="https://unpkg.com/reflect-metadata@0.1.3/Reflect.js"></script>
<script src="https://unpkg.com/systemjs@0.21.3/dist/system.js"></script>
<script src="config.js"></script>
<script>
System.import("app").catch(console.error.bind(console));
</script>
</head>
<body class="dx-viewport">
<div class="demo-container">
<demo-app>Loading...</demo-app>
</div>
</body>
</html>