title: Restsharp XML request
body: <p>I'm trying to PUT some data over an API with restsharp.</p>
  
  <p>From the manual of the API, the PUT call is made using:
  template params
  id  string
  barcode string</p>
  
  <p>and </p>
  
  <p>query params
  a   string
  operator    string
  c   long</p>
  
  <p>The request should have a custom header: Name = “Content-Type” Value = “application/xml”</p>
  
  <p>Can someone tell me how to use restsharp to post a request like this?</p>