title: @ContentChildren why cant I query Material Instances by Type
body: <p>Why cant I query material instances ???</p>
  
  <p><a href="https://stackblitz.com/edit/angular-a6ho6p?file=app/menu-overview-example.html" rel="nofollow noreferrer">STACKBLITZ</a></p>
  
  <h1>my *.html</h1>
  
  <pre><code>&lt;wMat-menu-group&gt;
  
    &lt;button mat-button [matMenuTriggerFor]="menu"&gt;Menu1&lt;/button&gt;
    &lt;mat-menu #menu="matMenu"&gt;
      &lt;button mat-menu-item&gt;Item 1&lt;/button&gt;
      &lt;button mat-menu-item&gt;Item 2&lt;/button&gt;
    &lt;/mat-menu&gt;
  
    ...
  
    &lt;button mat-button [matMenuTriggerFor]="menu3"&gt;Menu3&lt;/button&gt;
    &lt;mat-menu #menu3="matMenu"&gt;
      &lt;button mat-menu-item&gt;Item 5&lt;/button&gt;
      &lt;button mat-menu-item&gt;Item 6&lt;/button&gt;
    &lt;/mat-menu&gt;
  
  &lt;/wMat-menu-group&gt;
  </code></pre>
  
  <h1>my *.ts</h1>
  
  <pre><code>  @ContentChildren(MatMenuTrigger) mmtQL: QueryList&lt;MatMenuTrigger&gt;; // nope
    @ContentChildren(MatMenu) mmtQL2: QueryList&lt;MatMenu&gt;; // nope
    @ContentChildren(_MatMenu) mmtQL3: QueryList&lt;_MatMenu&gt;; //  nope
    @ContentChild('menu3', {static: true}) mm3: MatMenu; //  works
  </code></pre>
  
  <p>The only method that works is a <strong>NOT DYNAMIC ONE</strong> and therefore <strong>USELESS</strong>.</p>
  
  <p>Anyone has a hint?</p>