select all option functionality in angular 7 code example

Example: mat-select option to select all options

tosslePerOne(all){ 
   if (this.allSelected.selected) {  
    this.allSelected.deselect();
    return false;
}
  if(this.searchUserForm.controls.userType.value.length==this.userTypeFilters.length)
    this.allSelected.select();

}
  toggleAllSelection() {
    if (this.allSelected.selected) {
      this.searchUserForm.controls.userType
        .patchValue([...this.userTypeFilters.map(item => item.key), 0]);
    } else {
      this.searchUserForm.controls.userType.patchValue([]);
    }
  }
  
-------------------  HTML-----------

<form [formGroup]="searchUserForm" fxFlex fxLayout="column" autocomplete="off" style="margin: 30px">
    <mat-select placeholder="User Type" formControlName="userType" multiple>
        <mat-option *ngFor="let filters of userTypeFilters" [value]="filters.key" (click)="tosslePerOne(allSelected.viewValue)">
            {{filters.value}}
        </mat-option>
        <mat-option #allSelected (click)="toggleAllSelection()" [value]="0">All</mat-option>
    </mat-select>
</form>