Select * from Produto where code_product = textbox_code_product

I modified my code for

In GoLiveGlobals.infoMessageBox(nRowProjeto.ToString()); return 0 ! Why ?

I think that you are inadvertantly making a very simple task very complex.  As mentioned in previous posts, there are a lot of samples that show how to do this...and I know that other developers have tried to help you understand as well.  Maybe at this point you should just create a simple sample illustrating your problem and post it out here instead of all of these posts as this doesn't really seem to be going anywhere.  Maybe a real sample from YOUR perspective and then a correction via the forum posters will help you better undertstand where you are going wrong.