protected override void DoSaveSourceState(IVsaPersistSite site){
XmlDocument project = new XmlDocument();
project.LoadXml("<project></project>");
XmlElement root = project.DocumentElement;
this.SaveProjectVersion(project, root);
this.SaveVsaEngineState(project, root);
site.SaveElement(null, project.OuterXml);
this.SaveSourceForDebugging();
this.isEngineDirty = false;
}