A networked XML document is comprised of chunks of data aggregated using various W3C standard inclusion mechanisms and therefore contains nodes that come from different places. The BaseURI tells you where these nodes came from.

The value of this property varies depending on the node type. For example, Document nodes return the location of the System.Xml.XmlDocument object. Nodes which are child nodes of external EntityReference nodes return the location of the entity itself. For example, consider the following XML document:

 <!DOCTYPE item [
 <!ENTITY xyz SYSTEM "a/b.xml">
 ]>
 <item num='123'>&xyz;</item>

where the external entity a/b.xml contains the XML text: <test>123</test>.

If the document is loaded from http://server/mydata.xml, BaseURI returns the following:

BaseURI looks for entity reference boundaries, so if entities are expanded this information is not preserved and this property returns the location of the XmlDocument object in all cases.

As a second example, given the following XML document:

 <!DOCTYPE Mydata SYSTEM "http://localhost/doctype.dtd">
 <baa>&xyz;</baa>

where the DTD file contains the following:

 <!ENTITY xyz <E1>My Data</E1>
 <!ELEMENT baa #PCDATA>
 <!ATTLIST baa attr1 "woof">

If the XML document is loaded from http://localhost/mydata.xml, BaseURI returns the following for each of the nodes:

This property is a Microsoft extension to the Document Object Model (DOM).