title: XmlSerializer constructor with XmlTypeMapping and XmlRootAttribute arguments
body: <p>I'd like to prefetch in C#, the <code>XmlTypeMapping</code> of a known set of class types to speed up XML deserialization of them while instantiating a new <code>XmlSerializer</code> as <code>XmlReflectionImporter.ImportTypeMapping</code> (happening during <code>XmlSerializer</code> contruction on a class type) is quite time consuming and seem to happen at each <code>XmlSerializer</code> construction.</p>
  
  <p>In addition the xml content I am parsing forces me to use <code>XmlRootAttribute</code> argument to set the xml root element name to parse as it is not always the same. To achieve that, I can use the <code>XmlSerializer(Type, XmlRootAttribute)</code> constructor to deserialize my object.</p>
  
  <p>However I would also like to benefit from the prefetch <code>XmlTypeMapping</code> and I can't see any <code>XmlSerializer</code> constructor like : <code>XmlSerializer( XmlTypeMapping, XmlRootAttribute )</code> or something close. How could I achieve that?</p>
  
  <p>Any help would be greatly appreciated! Thanks.</p>