How To Bind DropDownList With Validation In Angular

In this article, we will learn about how we can bind the Drop-Down List in Angular and how to apply the required validation on it.

A Drop-Down List is a graphical control element, that allows the user to choose one value from a list. When a Drop-Down List is activated, it displays a list of values, from which the user may select one. When inactive, it displays a single value.

Prerequisites:

• Basic knowledge of Angular
• Code editor like Visual Studio Code

Create a new Angular project by typing the following command in the VSCode terminal.

ng new bind-dropdownlist

Open the app.component.ts file and add the code in it.

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  title = 'Bind DropDownList';
  products = [
    { id: 1, name: 'Smartphone' },
    { id: 2, name: 'Headphone' },
    { id: 3, name: 'Bike' },
    { id: 4, name: 'Laptop' },
    { id: 5, name: 'TV' },
    { id: 6, name: 'PC' },
    { id: 7, name: 'Car' }
  ];
}

Open the app.component.html file and add the HTML in it.

<h1>{{title}}</h1>
<select>
  <option *ngFor="let product of products" [value]="product.id">
    {{product.name}}
  </option>
</select>

Output:

Now please click the link given below and follow the steps to add Bootstrap 4 to Angular app for better and responsive design.

Add Bootstrap 4, jQuery and Font Awesome To Angular

Note: You must have to add jQuery because Bootstrap uses jQuery for JavaScript plugins.

Here, we are going to add the required field validation on the drop-down list.

Open the app.module.ts file then add the FormsModule in the file.

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import {FormsModule} from '@angular/forms';

import { AppRoutingModule } from './app-routing.module';
import { AppComponent } from './app.component';

@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule,
    AppRoutingModule,
    FormsModule,
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

Open the app.component.ts file and add the code in it.

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  title = 'Bind DropDownList';
  ddlProduct = "";
  products = [
    { id: 1, name: 'Smartphone' },
    { id: 2, name: 'Headphone' },
    { id: 3, name: 'Bike' },
    { id: 4, name: 'Laptop' },
    { id: 5, name: 'TV' },
    { id: 6, name: 'PC' },
    { id: 7, name: 'Car' }
  ];

  onSubmit() {
    alert('Product ID: ' + this.ddlProduct);
  }  
}

Now, just open the app.component.html and replace it with HTML given below.

<div class="container w-50">
  <h1>{{title}}</h1>
  <form name="form" (ngSubmit)="form.valid && onSubmit()" #form="ngForm">
    <div class="form-group">
      <label for="product">Product List</label>

      <!-- DropDownList -->
      <select class="custom-select" name="product" [(ngModel)]="ddlProduct" #product="ngModel"
        [ngClass]="{ 'is-invalid': form.submitted && product.invalid }" required>
        <option value="" class="text-primary font-weight-bolder">
          --- Select Product ---
        </option>
        <option *ngFor="let product of products" [value]="product.id">
          {{product.name}}
        </option>
      </select>
      
      <!-- Required Validation Message -->
      <div *ngIf="form.submitted && product.invalid" class="text-danger">
        <h6 *ngIf="product.errors.required">Product is Required</h6>
      </div>
    </div>
    <button class="btn btn-primary">Submit</button>
  </form>
</div>

That’s it.

Output:

Also, check Custom Searching In Angular