title: Appendheader needs to append string, variable and then string again
body: <p>Hopefully this is an easy one for someone out there. I need to append a long command that has strings and variables in it. </p>
  
  <pre><code>this-&gt;AppendHeader("Content-Range", "bytes " + offset "-" + (offset + part_size - 1) "/" + file_size);
  </code></pre>
  
  <p>This is not acceptable in C++. How can I format the above so the Header looks like</p>
  
  <pre><code>Content-Range: bytes 0-19/40
  </code></pre>
  
  <p>(just a fyi - offset is 0, part_size is 20 and file_size is 40)</p>