如何在mat-select中使用angular 6获取下拉文本

npm install --save @angular/material @angular/cdk @angular/animations

import { MatSelect } from '@angular/material';

selectedOption: string;

<mat-form-field>
  <mat-select [(ngModel)]="selectedOption">
    <mat-option value="option1">Option 1</mat-option>
    <mat-option value="option2">Option 2</mat-option>
    <mat-option value="option3">Option 3</mat-option>
  </mat-select>
</mat-form-field>

<mat-form-field>
  <mat-select [(ngModel)]="selectedOption" (change)="onOptionSelected()">
    <mat-option value="option1">Option 1</mat-option>
    <mat-option value="option2">Option 2</mat-option>
    <mat-option value="option3">Option 3</mat-option>
  </mat-select>
</mat-form-field>