How to determine the attached type from within a custom attribute?

问题

I have a custom attribute which can be assigned to a class, [FooAttribute]. What I would like to do, from within the attribute, is determine which type has actually used me. e.g. If I have:

[FooAttribute]
public class Bar
{
}

In the code for FooAttribute, how can I determine it was Bar class that added me? I'm not specifically looking for the Bar type, I just want to set a friendly name using reflection. e.g.

[FooAttribute(Name="MyFriendlyNameForThisClass")]
public class Bar
{
}

public class FooAttribute()
{
  public FooAttribute()
  {
    // How do I get the target types name? (as a default)
  }
}

回答1:

First off, you might consider the existing [DisplayName] for keeping friendly names. As has already been covered, you simply can't get this information inside the attribute. You can look up the attribute from Bar, but in general, the only way to do it from the attribute would be to pass the type into the attribute - i.e.

[Foo("Some name", typeof(Bar)]

What exactly is it you want to do? There may be other options...

Note that for i18n, resx, etc; you can subclass DisplayNameAttribute and provide lookup from keys by overriding the DisplayName getter.

回答2:

To elaborat. A attribute, built in or custom, is just meta data for a class, or class member, and the attribute itself nas no notation that it's being associated with something.

The type knows of it's own metadata
The meta data (in this case, the attribute) does not know to whom it belongs

回答3:

From your sentence "I just want to set a friendly name using reflection" I think you want to set the "MyFriendlyNameForThisClass" name to the attribute at runtime. if so, I don't think that's possible. Please see this thread.

回答4:

It is clumsy but you could iterate over all classes in the assembly, testing each for the custom attribute that "is" this instance.

来源：https://stackoverflow.com/questions/275855/how-to-determine-the-attached-type-from-within-a-custom-attribute

标签

.net

reflection

custom-attributes