Converting Datatable to xml string and viceversa

Question

XML is a simple and flexible system for defining data formats. This is completely platform independent and adopted everywhere for representing complex documents and data structures. For data transmission on web, its having significant contribution. 

It is very common to use dataset in .NET applications. A dataset may contain a single table or multiple tables that are related though primery and foreign keys. We can also use XML to completely reconstruct the dataset. Now days it's been the major use of XML to store both rowset (single table) and hierarchical (multiple-table) data in it.