Thanks for reply me.
I have a DataForm in a page. The navigation property use HyperlinkButton,when click the HyperlinkButton,then popup a Childwindow.
The Childwindow contain a GridView and a DomainDataSource, the DomainDataSource.DomainContext came from the page.
When the Childwindow closed, the DataForm in the page will get the GridView.SelectedItem to set DataForm.CurrentItem's navigation property..
The issue is:First click the HyperlinkButton to open the Childwindow is fine, the second time, the DomainDataSource in Childwindow LoadingData not raised.
The reason why use same DomainContext is: Can't set entity's navigation property,which from two different entitycontainer.