title: Angular 2 Material Select open with button
body: <p>I have a select dropdown that I want to open with a button click, there is no mention of this anywhere in the docs - I have tried using an element reference and using select.open() on the element but it doesn't work. Has anyone else run into this issue?</p>
  
  <pre><code>&lt;button ngClass="menu-filter-item-button" type="button" mat-button (click)="select.open()"&gt;
      &lt;strong class="menu-filter-item-title"&gt;{{filter.name}}&lt;/strong&gt;
      &lt;mat-icon&gt;keyboard_arrow_down&lt;/mat-icon&gt;
  &lt;/button&gt;
  &lt;mat-select #select multiple (change)="onSubmit($event)" [compareWith]="compareById" [(ngModel)]="filter.value"&gt;
      &lt;mat-option *ngFor="let value of filter.default" [value]="value"&gt;
          {{value}}
      &lt;/mat-option&gt;
  &lt;/mat-select&gt;
  </code></pre>