title: Form Validation not happening on angular 2 for input type="file"
body: <pre><code>  &lt;div class="form-group"&gt;
      &lt;label for="fileName"&gt;Name&lt;/label&gt;
  
      &lt;input type="file" class="form-control" id="fileName"  placeholder="Upload file" accept=".xlsx, .xls"
             required
             [(ngModel)]="model.fileName" name="fileName"
             #fileName="ngModel"&gt;
      &lt;div [hidden]="fileName.valid || fileName.pristine" class="alert alert-danger"&gt;
        File to be uploaded is required
      &lt;/div&gt;
    &lt;/div&gt;
  </code></pre>
  
  <p>Using angularjs2 forms, I am trying to upload a file and submit the form. Even if I choose the file, the control doesn't recognize the selected value.</p>