Impact of identical GUID across applications

Question

Whenever I have a new C# project, I often copy/rename an existing one in order to re-use most of the code. This means going into Assembly Info and renaming the project in there as well. In the past, I haven't really bothered with renaming the GUID.

Is this bad programming practice and could it negatively impact the user if they have another program open with the same GUID?

I am by no means an expert programmer, but I get by and I figure things out as I go along. Any advice would be welcome.

Answer 1

I would say blind copy/paste vs smart re-use is in general a bad practice, but if you update the values in the assemblyInfo you might be on the safe side.

Personally I always assign a different Guid to every project if I copy that file, but anyway the AssemblyGuid attribute is used only for COM interoperability so if you are making pure .NET class libraries or applications and you have ComVisible set to false because you don't expose anything via COM, you shouldn't worry and there wont be any impact on anything else.

Answer 2

If you are copy/pasting so often, consider extracting the common code into a library and referencing it from your other projects. This has advantages due the reduced maintenance when you make a change of fix a bug.