C#: How to use CategoryAttribute.Appearance Property

Question

I have read a bit about Design-Time Attributes for Components. There I found an attribute called CategoryAttribute. On that page it says that

The CategoryAttribute class defines the following common categories:

And then lists up a number of common categories. One of them are for example Appearance. I thought, brilliant! Then I can use [Category.Appearance] instead of [Category("Appearance")]! But apparently I couldn't? Tried to write it, but Intellisense wouldn't pick it up and it wouldn't compile. Am I missing something here? Was it maybe not this those properties were for? If not, what are they for? If they are, how do I use them?

And yes, I do have the correct using to have access to the CategoryAttribute, cause [Category("Whatever")] do work. I'm just wondering how I use those defined common categories.

score 4 · Accepted Answer · answered Mar 05 '09 at 14:40

As you can see on MSDN it's only a getter property, not a setter.

public static CategoryAttribute Appearance { get; }

In fact, here's what the code looks like using Reflector:

 public static CategoryAttribute Appearance
    {
        get
        {
            if (appearance == null)
            {
                appearance = new CategoryAttribute("Appearance");
            }
            return appearance;
        }
    }

So it doesn't do a heck of a lot.

The only use I can see for it, is something like this:

            foreach (CategoryAttribute attrib in prop.GetCustomAttributes(typeof(CategoryAttribute), false))
            {
                bool result = attrib.Equals(CategoryAttribute.Appearance);
            }

Basically, when using reflection to look at the class, you can easily check which category this belongs to without having to do a String comparison. But you can't use it in the manner you're trying to unfortunately.

hm, that's just plain annoying... hehe. what's the point in a constant defined attribute when it is only usable in one end. Oh well. Thanks for the info :) — Svish, Mar 05 '09 at 21:19
May be you could create your own Categories Class. Take a look [here](http://weblogs.asp.net/sfeldman/archive/2009/05/07/categoryattribute.aspx) — Ivan Ferrer Villa, Nov 09 '11 at 11:34

score 2 · Answer 2 · answered Mar 05 '09 at 14:33

The static property is accessed via CategoryAttribute.Appearance. But the attribute system does not allow you to invoke code in an attribute declaration and I guess that is why it wont compile for you. You will probably have to settle for [Category("Appearance")].

score 0 · Answer 3 · answered Jun 11 '22 at 18:46

0

Starting from C# 6 there is finally a better alternative: [Category(nameof(CategoryAttribute.Appearance))].

answered Jun 11 '22 at 18:46

glopes

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C#: How to use CategoryAttribute.Appearance Property

3 Answers3