title: PrimeNG manually invoke FileUpload
body: <p>I want to select the files first and then to start upload those files by an another button instead of component's own <code>Upload</code> button.</p>
  
  <p>How can I do this?</p>
  
  <p><strong>Example code what I've tried:</strong></p>
  
  <pre><code>&lt;button pButton type="button" label="Start Upload"
          (click)="startUpload()"&gt;&lt;/button&gt;
  
  &lt;p-fileUpload #fileInput name="fileIcon"
                url="rest/batch/file/multimedia/"&gt;&lt;/p-fileUpload&gt;
  
  
  @ViewChild('fileInput') fileInput:ElementRef;
  
  constructor( private renderer: Renderer ) { }
  
  startUpload(){
  
      // this.fileInput.upload(); -&gt; doesn't compile, undefined
      // this.fileInput.nativeElement.upload(); -&gt; this.fileInput.nativeElement is undefined
  
      ?????????????????
  }
  </code></pre>