Can not display nodes after setting their location

I have set X,Y position for a node which is on some link,
After saved chart I’m sure the data has been saved into database, also have a data Binding of Node.location
But after called diagram.rebuildParts(),
chart nodes do not displayed on the given X,Y position. Need help.

If those nodes are label nodes, in that they are each owned by a Link and Node | GoJS API is true, then you need to set or bind not the Node.location, but one or more of the link label properties described at GoJS Link Labels -- Northwoods Software

Thanks a lot, that’s what i need.