D-Net

import {Directive, Input, OnInit} from "@angular/core";

import {MatSelect} from "@angular/material/select";

@Directive({

  selector: '[modal-select]'

})

export class ModalSelectDirective implements OnInit{

  @Input() matSelect: MatSelect;

  ngOnInit() {

    this.matSelect._openedStream.subscribe( () => {

      let divElement: HTMLDivElement = <HTMLDivElement>document.getElementsByClassName('cdk-overlay-container')[0];

      divElement.classList.add('modal-select');

    });

  }

}