System.IO.StringWriter writer = new System.IO.StringWriter();
dataTable.WriteXml(writer, XmlWriteMode.WriteSchema, false);
string xmlFromDataTable = writer.ToString();
 

Use XmlWriteMode.WriteSchema to include the schema in the output.
 

I like things that are easy to implement and that complement the end users experience.  I think I’ve found one that fits this perfectly.  Most users want the option to change the number of records on a show table page and would like the system to remember it the next time they visit the page.  The control Pagination.ascx in the shared folder is common to every show table page and is the perfect candidate to implement this type of functionality.