title: cURL call in C# with flag
body: <p>I'd like to make a following curl call in C#:</p>
  
  <pre><code>curl "http://localhost:8983/solr/update/extract?literal.id=doc1&amp;commit=true" -F "myfile=@tutorial.html"
  </code></pre>
  
  <p>I found that I should use WebRequest class, but I'm still not sure how deal with this part:</p>
  
  <pre><code>-F "myfile=@tutorial.html"
  </code></pre>