through custom validation error in alravel code example

Example 1: if any error in blade laravel

@if ($errors->any())
     @foreach ($errors->all() as $error)
         <div>{{$error}}</div>
     @endforeach
 @endif

Example 2: how to add an custom error to validater error in laravel

if (request('event') == null) {
    $validator->errors()->add('event', 'Please select an event');
}