Foreground object

I have need to make the following thing: do I have to succeed in putting in the foreground always an object as I can do?

I’m sorry, but I do not understand what you want to do. Could you describe what you need again? Perhaps you can refer to a sample application that does something similar.

Normally you can make sure an object is in front of other objects by moving it into a separate layer that you have created to be in front of the other document layers. Initialize your document by:
goView1.Document.Layers.CreateNewLayerAfter(null);
This creates a new GoLayer that you can get via the property:
goView1.Document.Layers.Top
You can "move" a top-level GoObject from one layer to another by just Add'ing it to the desired GoLayer.
The Classier sample, for example, moves selected nodes into the Top layer; deselected nodes get moved back to the DefaultLayer. This can be implemented in GoView.ObjectGotSelection and ObjectLostSelection event handlers; in the Classier sample, it's actually implemented as overrides of GoObject.OnGotSelection and OnLostSelection in the node class.