Описание тега xmldatasource

The XmlDataSource control can be used by data-bound controls to display both hierarchical and tabular data. The XmlDataSource control is typically used to display hierarchical XML data in read-only scenarios. Because the XmlDataSource control extends the HierarchicalDataSourceControl class, it works with hierarchical data. The XmlDataSource control also implements the IDataSource interface and works with tabular, or list-style, data.

System.Object   
  System.Web.UI.Control  
    System.Web.UI.HierarchicalDataSourceControl  
      System.Web.UI.WebControls.XmlDataSource   
Namespace:  System.Web.UI.WebControls    
Assembly:  System.Web (in System.Web.dll)  

http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.xmldatasource%28v=vs.110%29.aspx