Can't bind to 'ngForOf' since it isn't a known property of 'mat-expansion-panel' code example

Example 1: Can't bind to 'ngForOf' since it isn't a known property of 'div'.

// older Angular versions
// import {BrowserModule, CommonModule} from '@angular/common';

import { BrowserModule } from '@angular/platform-browser'
..
..
@NgModule({
  imports: [BrowserModule, /* or CommonModule */],
  ..
})

Example 2: Can't bind to 'ngForOf' since it isn't a known property of 'th'

// resolved by importing CommonModule not on the app.module.ts but 
// on the componentName.module.ts

import { CommonModule } from '@angular/common';
imports: [CommonModule]