DataSet to XmlDocument and Back

To convert your DataSet into an XmlDocument:

MyDataSet myDataSet = new MyDataSet();
// Add rows to the DataTables in myDataSet

XmlDocument myXmlDocument = new XmlDocument();
myXmlDocument.LoadXml(myDataSet.GetXml());

To convert your XmlDocument into a DataSet:

MyDataSet myDataSet = new MyDataSet();

myDataSet.ReadXml(new MemoryStream((new UTF8Encoding()).GetBytes(myXmlDocument.OuterXml)));

More Info:MSDN: XmlDocument.LoadXml Method
MSDN: DataSet.ReadXml Method (Stream)