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Data Binding in Angular MultiSelect component

25 Oct 2021 / 6 minutes to read

The MultiSelect loads the data either from local data sources or remote data services using the dataSource property. It supports the data type of array or DataManager.

The MultiSelect also supports different kinds of data services such as OData, OData V4, and Web API, and data formats such as XML, JSON, and JSONP with the help of DataManager adaptors.

Fields Type Description
text string Specifies the display text of each list item.
value number or string Specifies the hidden data value mapped to each list item that should contain a unique value.
groupBy string Specifies the category under which the list item has to be grouped.
iconCss string Specifies the icon class of each list item.

When binding complex data to the MultiSelect, fields should be mapped correctly. Otherwise, the selected item remains undefined.

Binding local data

Local data can be represented in two ways as described below.

1. Array of string

The MultiSelect has support to load array of primitive data such as strings and numbers. Here, both value and text field act the same.

Source
Preview
app.component.ts
app.module.ts
main.ts
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import { Component } from '@angular/core';

@Component({
selector: 'app-root',
// specifies the template string for the MultiSelect component with dataSource
template: `<ejs-multiselect id='multiselectelement' [dataSource]='sportsData' [placeholder]='placeholder'></ejs-multiselect>`
})
export class AppComponent {
constructor() {
}
// defined the array of data
public sportsData: string[] = ['Badminton', 'Cricket', 'Football', 'Golf', 'Tennis'];
// set placeholder to MultiSelect input element
public placeholder: string = 'Select games';
}
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import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';
import { AppComponent } from './app.component';
import { MultiSelectModule } from '@syncfusion/ej2-angular-dropdowns';
import { ButtonModule } from '@syncfusion/ej2-angular-buttons';
/**
 * Module
 */
@NgModule({
    imports: [
        BrowserModule,FormsModule, ReactiveFormsModule, MultiSelectModule, ButtonModule
    ],
    declarations: [AppComponent],
    bootstrap: [AppComponent]
})
export class AppModule { }
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import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
import { enableProdMode } from '@angular/core';
import { AppModule } from './app.module';

enableProdMode();
platformBrowserDynamic().bootstrapModule(AppModule);

2. Array of object

The MultiSelect can generate its list items through an array of complex data. For this, the appropriate columns should be mapped to the fields property.

In the following example, id column and sports column from complex data have been mapped to the value field and text field, respectively.

Source
Preview
app.component.ts
app.module.ts
main.ts
Copied to clipboard
import { Component } from '@angular/core';
@Component({
selector: 'app-root',
// specifies the template string for the MultiSelect component
template: `<ejs-multiselect id='multiselectelement' [dataSource]='sportsData' [fields]='fields'[placeholder]='placeholder'></ejs-multiselect>`
})
export class AppComponent {
constructor() {
}
//set the data to dataSource property
public sportsData: Object[] =  [
    { id: 'Game1', sports: 'Badminton' },
    { id: 'Game2', sports: 'Basketball' },
    { id: 'Game3', sports: 'Cricket' },
    { id: 'Game4', sports: 'Football' },
    { id: 'Game5', sports: 'Golf' }
];
// maps the appropriate column to fields property
public fields: Object = { text: 'sports', value: 'id' };
// set placeholder to MultiSelect input element
public placeholder: string = 'Select games';
}
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import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';
import { AppComponent } from './app.component';
import { MultiSelectModule } from '@syncfusion/ej2-angular-dropdowns';
import { ButtonModule } from '@syncfusion/ej2-angular-buttons';
/**
 * Module
 */
@NgModule({
    imports: [
        BrowserModule,FormsModule, ReactiveFormsModule, MultiSelectModule, ButtonModule
    ],
    declarations: [AppComponent],
    bootstrap: [AppComponent]
})
export class AppModule { }
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import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
import { enableProdMode } from '@angular/core';
import { AppModule } from './app.module';

enableProdMode();
platformBrowserDynamic().bootstrapModule(AppModule);

2. Array of complex object

The MultiSelect can generate its list items through an array of complex data. For this, the appropriate columns should be mapped to the fields property.

In the following example, Code.Id column and Country.Name column from complex data have been mapped to the value field and text field, respectively.

Source
Preview
app.component.ts
app.module.ts
main.ts
Copied to clipboard
import { Component } from '@angular/core';

@Component({
selector: 'app-root',
// specifies the template string for the MultiSelect component
template: `<ejs-multiselect id='multiselectelement' [dataSource]='sportsData' [fields]='fields'[placeholder]='placeholder'></ejs-multiselect>`
})
export class AppComponent {
constructor() {
}
//set the data to dataSource property
public sportsData: Object[] =  [
    { Country: { Name: 'Australia' }, Code: { Id: 'AU' }},
    { Country: { Name: 'Bermuda' },Code: { Id: 'BM' }},
    { Country:{ Name: 'Canada'}, Code:{ Id: 'CA'} },
    { Country:{Name: 'Cameroon'}, Code:{ Id: 'CM'} },
    { Country:{Name: 'Denmark'}, Code:{ Id: 'DK' }},
    { Country:{Name: 'France'}, Code: { Id:'FR'} }
];
// maps the appropriate column to fields property
public fields: Object = { text: 'Country.Name', value: 'Code.Id' };
// set placeholder to MultiSelect input element
public placeholder: string = 'Select a country';
}
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import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';
import { AppComponent } from './app.component';
import { MultiSelectModule } from '@syncfusion/ej2-angular-dropdowns';
import { ButtonModule } from '@syncfusion/ej2-angular-buttons';
/**
 * Module
 */
@NgModule({
    imports: [
        BrowserModule,FormsModule, ReactiveFormsModule, MultiSelectModule, ButtonModule
    ],
    declarations: [AppComponent],
    bootstrap: [AppComponent]
})
export class AppModule { }
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import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
import { enableProdMode } from '@angular/core';
import { AppModule } from './app.module';

enableProdMode();
platformBrowserDynamic().bootstrapModule(AppModule);

Binding remote data

The MultiSelect supports retrieval of data from remote data services with the help of DataManager component. The Query property is used to fetch data from the database and bind it to the MultiSelect.

The following sample displays the first 6 contacts from “Customers” table of the Northwind Data Service.

Source
Preview
app.component.ts
app.module.ts
main.ts
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import { Component } from '@angular/core';
//import DataManager related classes
import { Query, DataManager, ODataV4Adaptor } from '@syncfusion/ej2-data'

@Component({
selector: 'app-root',
// specifies the template string for the MultiSelect component
template: `<ejs-multiselect id='multiselectelement' [dataSource]='data' [fields]='fields' [placeholder]='placeholder' [query]='query' [sortOrder]='sorting'></ejs-multiselect>`
})
export class AppComponent {
constructor() {
}
//bind the DataManager instance to dataSource property
public data: DataManager = new DataManager({
        url: 'https://services.odata.org/V4/Northwind/Northwind.svc/',
        adaptor: new ODataV4Adaptor,
        crossDomain: true
});
// maps the appropriate column to fields property
public fields: Object = { text: 'ContactName', value: 'CustomerID' };
//bind the Query instance to query property
public query: Query = new Query().from('Customers').select(['ContactName', 'CustomerID']).take(5);
// set placeholder to MultiSelect input element
public placeholder: string = 'Select customers';
//sort the result items
public sorting: string = 'Ascending';
}
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import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';
import { AppComponent } from './app.component';
import { MultiSelectModule } from '@syncfusion/ej2-angular-dropdowns';
import { ButtonModule } from '@syncfusion/ej2-angular-buttons';
/**
 * Module
 */
@NgModule({
    imports: [
        BrowserModule,FormsModule, ReactiveFormsModule, MultiSelectModule, ButtonModule
    ],
    declarations: [AppComponent],
    bootstrap: [AppComponent]
})
export class AppModule { }
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import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
import { enableProdMode } from '@angular/core';
import { AppModule } from './app.module';

enableProdMode();
platformBrowserDynamic().bootstrapModule(AppModule);

Data binding using Async pipe

An Observable is used extensively by Angular since it provide significant benefits over techniques for event handling, asynchronous programming, and handling multiple values.

MultiSelect data can be consumed from an Observable object by piping it through an async pipe. The async pipe is used to subscribe the observable object and resolve with the latest value emitted by it.

Source
Preview
app.component.ts
app.module.ts
main.ts
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import { Component } from '@angular/core';
import { Observable } from 'rxjs';
import { CategoriesService } from './categories.service';
import { map } from 'rxjs/operators';
import { HttpClient } from '@angular/common/http';

@Component({
selector: 'app-root',
// specifies the template string for the Multiselect component with dataSource
template: `<ejs-multiselect  id='customers2' formControlName="skillname" name="skillname" #remote2 [dataSource]='data | async'  [fields]='remoteFields' [placeholder]='remoteWaterMark' ></ejs-multiselect >`,
providers: [CategoriesService]
})
export class AppComponent {
constructor(private http: HttpClient){
  this.data=this.http.get<{[key: string]:object;}[]>('https://services.odata.org/V4/Northwind/Northwind.svc/Customers').pipe(
  map((results : {[key: string]:object;}) => {
    return results.value;
  })
);
  }

 public data: Observable<any>;

  // maps the remote data column to fields property
  public remoteFields: Object = { value: 'CustomerID' };

  // set the placeholder to Multiselect input element
  public remoteWaterMark: string = 'Select a customer';
}
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import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { FormsModule } from '@angular/forms';
import { HttpClientModule } from '@angular/common/http';
import { DropDownListModule, MultiSelectModule} from '@syncfusion/ej2-angular-dropdowns';
import { AppComponent } from './app.component';
import { HelloComponent } from './hello.component';
import {DialogModule} from '@syncfusion/ej2-angular-popups';
import { HttpModule, JsonpModule } from '@angular/http';
import { ReactiveFormsModule }   from '@angular/forms';
@NgModule({
  imports: [ 
    BrowserModule, 
    FormsModule,
    DropDownListModule,
    MultiSelectModule,
    DialogModule,
    HttpClientModule,
    ReactiveFormsModule, HttpModule, JsonpModule
    ],
  declarations: [ AppComponent, HelloComponent ],
  bootstrap:    [ AppComponent ]
})
export class AppModule { }
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import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
import { enableProdMode } from '@angular/core';
import { AppModule } from './app.module';

enableProdMode();
platformBrowserDynamic().bootstrapModule(AppModule);

See Also