I had thought that this was one of the few solved problems in C# coding standards / style; Attributes always appear on the line above the thing to which they are applied a la

class SomeClass
   bool someField;


   void SomeMethod() 

But recently I've started to see Attributes in-line with the thing to which they are applied:

[SomeClassAttribute] class SomeClass
   [SomeFieldAttribute] bool someField;

   [SomeEnumAttribute] SomeEnum

   [SomeMethodAttribute] void SomeMethod() 

For example on the Microsoft website and in the FileHelpers open source project. Is this just laziness on the part of the author of example code, or something that people actually use on a day to day basis, and if so why?

  • That's interesting: I've not previously come across such placement. – BoltClock Apr 16 '11 at 11:49
  • Purely stylistic. That being said, I can't imagine using anything but the first style... – Cody Gray Apr 16 '11 at 11:55
  • Me neither, when I saw it on the FileHelpers site I thought it was an aberration, but seeing it on the Microsoft site for a new .Net attribute made me wonder. – B Tyler Apr 16 '11 at 11:56
  • Note that there is one case where attributes are usually written inline: method parameter attributes, such as void Foo([In] string s). – svick Apr 16 '11 at 12:42
  • @svick Good point – B Tyler Apr 16 '11 at 13:09

You can't put the attribute on the line above if it's being applied to a parameter.

e.g. this example from an ASP.NET MVC book

public ViewResult List([DefaultValue(1)] int page)
    // ... 

Maybe this has led to some people choosing to write attributes inline?

Also another example involving LINQ to SQL mappings..

[Column] public string Name { get; set; }
[Column] public string Description { get; set; }
[Column] public decimal Price { get; set; }
[Column] public string Category { get; set; }

The [Column] attribute almost feels like another modifier like the public access or the type, I can see how it might feel comfortable to write it inline like that.

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  • I think that you could put it above though for a method parameter, it's just that it might get a bit clunky. – B Tyler Apr 16 '11 at 13:11
  • @B Tyler - yep I suppose there's no reason to have all your parameters on one line of code, you could put them on separate lines with attributes above. Probably would violate some other code style rules, though! :-) – Carson63000 Apr 16 '11 at 22:08

The two pieces of code are identical. It's merely a styling choice.

I've always preferred the former style, so I'll keep doing that. Use the convention that is easier for you and your team.

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The first method is preferred - you may have several attributes, and some of them very long, for example:

 [DebuggerDisplay("Collection with {Count} elements of {User} user")]
 ... some security attributes ...
 ... some application specific attributes ...
 ... some resharper attributes ...

I have no idea on how to write them in one line and maintain readability...

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  • With a comma, perhaps? – Cody Gray Apr 16 '11 at 12:09
  • I didn't really mean that to sound like a question. The actual answer is to separate each attribute with a comma. This issue has already been solved. – Cody Gray Apr 17 '11 at 4:45

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