Help needed in Radio Button validation

[option donna]

Hello, 

i am new to angular and my current office project is in angular 6. i need to validate the radio button on button click. below is the code. but its not working. any help will be highly appreciated

<fieldset class="opt-out-prompt">

        <span *ngIf="editMode==='del'>

          <p>months you don't need this order?</p>

          <input type="radio" formControlName="actionType"  name="actionType" role="radiogroup" id="deleteorder">

          <label for="deleteorder"> No, please delete my order altogether</label>

          <br>

          <input type="radio" formControlName="actionType" name="actionType" role="radiogroup" id="optoutmonth" >

          <label for="optoutmonth"> Yes, show me opt-out months</label>

        </span>

        <div *ngIf="submittedOnce && cartForm.errors?.required">

          <p>Please select either value</p>

       </div>

      </fieldset>

.TS Code :

CartOptionForm = this.fb.group({

    actionType: ['', [Validators.required]]

  })

  get cartForm() {

    return this.CartOptionForm.get('actionType');

  }

 onSubmit() {

    this.submittedOnce = true;

    

    if (this.isFormValid()) {

       // success

    }

  }

isFormValid(): boolean {

    

    if(!this.CartOptionForm.valid) {

      return false;

    }

 else

{

 

    return true

}

}