How to save the text of a document range in different formats

This example illustrates API methods used to get the text of the document range in different formats - RTF, HTML, MHT, DOCX.
Although the preferable technique to save the document in different formats is the SaveDocument and the SaveDocumentAs methods, several methods allow obtaining text of the specified range in different formats. Current example provides code snippets which use these methods. Note the implementation of the IUriProvider interface required for HTML export.