public WOPIMessageEncoder(WOPIMessageEncoderFactory factory)
{
TextMessageEncodingBindingElement element = new TextMessageEncodingBindingElement();
element.MessageVersion = factory.MessageVersion;
element.WriteEncoding = Encoding.GetEncoding(factory.CharSet);
this.innerEncoder = element.CreateMessageEncoderFactory().Encoder;
this.factory = factory;
this.contentType = string.Format("{0}; charset={1}", "text/xml", this.factory.CharSet);
}