title: ASP.NET MVC FileResult to file on disk
body: <p>For my mocking purposes I'd like to output a FileResult to an actual file on disk. </p>
  
  <p>Is there a way to get the contents of a FileResult and write it to a file?
  The exposed properties on a FileResult are a bit on the slim side.</p>
  
  <p>I'm looking for something like:</p>
  
  <pre><code>var file_result = controller.CsvExport();
  
  file_result.ToFile(@"C:\temp.csv");
  
  public static void WriteToFile(this FileResult fileResult, string fileName)
  {
      // what to implement here?
      [...]
  }
  </code></pre>