I was able to successfully Add Select All
functionality when checkbox is clicked. However I am unable to Uncheck All
when all items are already selected
Here is the link to code - https://stackblitz.com/edit/angular-material-select-all-aota2app.component.html
Your function unselectAll()
has never been called
<mat-checkbox (ngModelChange)="selected = !selected" [ngModel]="checked">Check/ Uncheck</mat-checkbox>