CSS validations on dropdown

[yogesh-mali44]

Is there a way to add bootstrap validations in Angular 2 multi-select dropdown. Basically is is possible to highlight the dropdown in red if user does not select any values like for a normal input I can use [ngClass]="{'is-invalid': someThing.invalid}".

I saw the template drive form example but it does not give a way to do the above.

[devglen]

I need the same ability, but probably going to end up writing custom CSS to achieve this.