Question: I am using C# having come from a Java background - I have an exception but it does not tell me the line number - Just the method name.

Is that usual?? Is it down to Debug / Release builds??

Answer: 
This is down to debug symbols not being available - when you build your project make sure that you have "full" set in the debug settings (`Project properties` -> `Build` -> `Advanced` -> `Debug info`) and also make sure that the resulting pdb files are present alongside the assmebly in the same directory when you are running your app.
Make sure the PDB files of your application are deployed with the application. The PDB files are the files that is used by the CLR to determine the source code line numbers.