Is there an advantage to using IsDefined over GetCustomAttributes

Question

Consider the case when the assembly contains one or more types associated with the MyAttribute user attribute, and you need to get a list of these types. Is there any benefit to using IsDefined against GetCustomAttributes besides a more compact syntax? To show / hide what the other does not have? Is more effective than the other?

Here is a sample code demonstrating each use:

 Assembly assembly = ... var typesWithMyAttributeFromIsDefined = from type in assembly.GetTypes() where type.IsDefined(typeof(MyAttribute), false) select type; var typesWithMyAttributeFromGetCustomAttributes = from type in assembly.GetTypes() let attributes = type.GetCustomAttributes(typeof(MyAttribute), false) where attributes != null && attributes.Length > 0 select type; 

Answer 1

A quick quick test with two methods, and it seems that IsDefined much faster than GetCustomAttributes

200,000 iterations

 IsDefined average Ticks = 54 GetCustomAttributes average Ticks = 114 

Hope this helps :)

Answer 2

As Saddam shows, IsDefined more efficient than GetCustomAttributes . This is to be expected.

As described here , applying the MyAttribute attribute to the MyClass class is conceptually equivalent to instantiating the MyAttribute . However, instantiation does not actually occur unless MyClass is requested for attributes, as with GetCustomAttributes .

IsDefined , on the other hand, does not instantiate MyAttribute .