CODEWITHSUNDEEP
c#attributescustom-attributes
patrick
patrick

Reputation: 16959

Equivalent of typeof(class) for custom attribute

Is there an equivalent of typeof( ) for a custom attribute?

Specifically I would like to rewrite this code in such a way where I wouldn't rely on string comparison

if (prop.GetCustomAttributes(true).Any(c => c.GetType().Name == "JsonIgnoreAttribute")) { ... }

Upvotes: 0

Views: 1537

Answers (2)

Lucas Trzesniewski
Lucas Trzesniewski

Reputation: 51330

There is an overload of GetCustomAttributes which takes the type you want as a parameter:

prop.GetCustomAttributes(typeof(JsonIgnoreAttribute), true)

But as you're actually checking for the presence of the attribute, you should rather use the IsDefined function:

if (Attribute.IsDefined(prop, typeof(JsonIgnoreAttribute), true))

This does not instantiate the attributes, and is therefore more performant.

If you didn't need the inherit parameter, you could have written:

if (prop.IsDefined(typeof(JsonIgnoreAttribute)))

For some reason, this parameter is ignored in the MemberInfo.IsDefined function of properties and events, but taken into account in Attribute.IsDefined. Go figure.

Note that any type assignable to JsonIgnoreAttribute will be matched by these functions, so derived types will also be returned.

As a side note, you could have directly compared the Type objects like this:
c.GetType() == typeof(JsonIgnoreAttribute) (is it the exact same type?),
or c is JsonIgnoreAttribute (is the type assignable?).

Upvotes: 3

JLRishe
JLRishe

Reputation: 101690

What's wrong with using typeof()? or better yet, is?

if (prop.GetCustomAttributes(true).Any(c => c is JsonIgnoreAttribute))

You could also do:

if (prop.GetCustomAttributes(true).OfType<JsonIgnoreAttribute>().Any())

or 

if (prop.GetCustomAttributes(typeof(JsonIgnoreAttribute), true).Any())

Upvotes: 2

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