Using variables within Attributes in C#

Question

We have some Well-Attributed DB code, like so:

[Display(Name = "Phone Number")]
public string Phone { get; set; }

Since it is quite generic we'd like to use it again, but with a different string in the Name part of the attribute. Since it's an attribute it seems to want things to be const, so we tried:

const string AddressType = "Student ";
[Display(Name = AddressType + "Phone Number")]
public string Phone { get; set; }

This seems to work alright, except that having a const string means we can't overwrite it in any base classes, thereby removing the functionality that we originally were intending to add, and exposing my question:

Is there a way to use some sort of variable inside of an attribute so that we can inherit and keep the attribute decorations?

Daniel Renshaw · Accepted Answer · 2010-05-13 15:02:18Z

33

Everything inside an attribute must be known to the compiler at compile-time. Variables are inherently variable (!) so can't be used in attributes.

If you can use a code generation tool, you'd be able to dynamically inject different (constant) values into each derived class.

answered May 13, 2010 at 15:02

Daniel Renshaw

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4 Comments

thepaulpage Over a year ago

That's too bad, but I figured as such. Thanks.

liang Over a year ago

That's too bad indeed. However, there should be such use cases, are there nice alternatives?

lucidbrot Over a year ago

Does this also justify why we cannot use a static readonly String as attribute argument? Edit: Nevermind, we can use a const String.

AleX_ Over a year ago

Can we use stuff defined in appsettings.json?

Adam Robinson · Accepted Answer · 2010-05-13 15:02:48Z

4

You could jump through hoops and use an additional attribute to define the variable portion, but that would be quite a bit of work compared to what it would produce. There's no simple way to accomplish what you're after.

answered May 13, 2010 at 15:02

Adam Robinson

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1 Comment

thepaulpage Over a year ago

I briefly considered my own attribute, but I think the extra work would not justify the saved work. It's a simple problem on my end of things, but not when it has to be compiled.

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