Cannot set a value on node type 'Element'

This error occurs if you wrongly use the Value property of XmlNode to change the value of an element.

XmlDocument xdoc = new XmlDocument();
xdoc.Load( MapPath( "XmlSample.xml" ) );
XmlNode node =
xdoc.SelectSingleNode( "//element[@id=100]" );

// The following line will lead to
// an InvalidOperationException
node.Value = "New value!!";

xdoc.Save( MapPath( "XmlSample.xml" ) );

Instead, use the InnerText property:

node.InnerText = "New value!!";

[Edited: 4 Aug 2008]