title: Cannot assign to 'value' because it is a constant or a read-only property. Angular 6
body: <p>I am trying to set a value to a Mat input using FormControl</p>
  
  <pre><code>&lt;input name="contact" matInput [matAutocomplete]="contactAuto"  [formControl]="myControl" #contact (blur)="validateInput($event, contact.value)"  &gt;
  </code></pre>
  
  <p>In my Ts</p>
  
  <pre><code>myControl = new FormControl();
  this.myControl.value = 'contact';
  </code></pre>
  
  <p>The above code is working fine but I get an error </p>
  
  <pre><code>Cannot assign to 'value' because it is a constant or a read-only property
  </code></pre>
  
  <p>Am I missing something here?</p>