One class per file rule in .NET? [closed]

Answer 1

Really, this boils down to personal preference. Everybody will say "one class per file", but we all have our reasons for avoiding that in certain circumstances. I used to have a large project that had about 300 different enums. No way am I going to have 300 seperate files, one for each class, when some of the enums only were tri-state.

Also for people that can't find certain classes if they aren't all in files named after what they are, is there a reason you don't use Find looking in the entire solution? Using Find saves me valuable time scrolling through Solution Explorer.

Answer 2

In larger solutions I think it is very valuable to have one class per file and that the file is named the same thing as the class. It makes it much easier to locate the code you need to work in.

Answer 3

I only do this rarely. For example if there is an enumeration or struct that is closely related to the class yet too trivial to be separated on its own.

Or a separate class to contain some extension methods for that main class.

Answer 4

One reason for putting multiple related classes in one file is so that the poor bastard who uses your API doesn't have to spend half a day typing import declaration boilerplate and the poor bastard who has to maintain the code doesn't have to spend half a day scrolling through import declaration boilerplate. My rule of thumb is that multiple classes belong in the same file if you would almost always use a large subset of them at the same time instead of just one at a time.

Answer 5

Another point I have not seen anyone else mention is that when you develop using the one class per file rule you can easily see what that specific class is using.

For example: you may have two classes where one class uses Linq and the other does not.

If these classes were in the same file you would not be able to tell without looking through the code which class uses what. When it is one class per file all you have to do is look at the top of the file to see exactly what is being used in that class. Helps if you are ever migrating over to a new lib etc.

Answer 6

No matter how lightweight the content, I think one class / interface / etc. per file is essential.

If I'm working on a big solution in Visual Studio I want to be able to see the files and not have to delve inside to see. Even with navigation tools like ReSharper, I want a 1:1 mapping.

If you find a lot of source files with little or no content (maybe extending a class but adding nothing to it) then perhaps you should rethink your design.