Dynamischer Satz in Angular unter Verwendung von FormControl erforderlich

onAddValidationClick(){
    this.formGroup.controls["firstName"].setValidators(Validators.required);
    this.formGroup.controls["firstName"].updateValueAndValidity();
}

onRemoveValidationClick(){
    this.formGroup.controls["firstName"].clearValidators();
    this.formGroup.controls["firstName"].updateValueAndValidity();
}
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