This is what i have in the startup
public void InternalStartup()
{
((ButtonEvent)EventManager.ControlEvents["btnSaveBuilding"]).Clicked += new ClickedEventHandler(btnSaveBuilding_Clicked);
WindowsIdentity objcurrentIdentity = WindowsIdentity.GetCurrent();
XPathNavigator objRoot = this.MainDataSource.CreateNavigator();
XPathNavigator objXnDoc = this.MainDataSource.CreateNavigator();
string strUserInfo="";
strUserInfo = objcurrentIdentity.Name;
objRoot.SelectSingleNode("/my:AddBuilding/my:txtUserInfo", this.NamespaceManager).SetValue(strUserInfo);
}