[ Version ( since = "0.2.0" ) ]
public string etag { get; construct; }
An identifier for a particular version of the entry.
This changes every time the entry on the server changes, and can be used for conditional retrieval and locking.
For more information, see the <ulink type="http" url="http://code.google.com/apis/gdata/docs/2.0/reference.html#ResourceVersioning" > GData specification</ulink>.