Needing a few minor alterations done we have asked a previous developer we have used to make the necessary amendments but they have reported the following problems with the source code:

when we are using the source file without using the dll file its getting error.
we are using the class file of Data layer, the namespaces are not matching and it giving error.
Then we tried to change the namespaces but in some pages the 'ambigious dotnetnuke.data namespaces' error is arrised.

Any suggestions on what is going wrong?