How to use reflection to find certain classes in an assembly?

Question

If I have a .Net assembly loaded and I want to use reflection to find the classes (types) decorated with some attribute, eg

[MyClassAttribute]
public SomeClass
{
}

how do I do it in C#? I have got as far as

Assembly assy = Assembly.Load(assyPath);
var classesInAssy = assy.GetTypes();

but thereafter I'm stumped. I now know I have to use the CustomAttibutes collection on the type, but I'm using VS2013 Pro (which includes unit testing), and the attribute in question isn't one of mine but the MS TestClass attribute. However I can't seem to reference the assembly it is defined in (Microsoft.VisualStudio.QualityTools.UnitTestFramework.dll) even though the dll is listed in the Add References dialog in VS2013. Am I missing something?

TIA,

score 0 · Answer 1 · answered Jul 10 '15 at 15:43

0

An alternative to Jon Skeet's answer is to use GetCustomAttributes:

Type[] classesWithAttr = assy.GetTypes()
    .Where(t => t.GetCustomAttributes(typeof(MyClassAttribute), false).Length > 0)
    .ToArray();

answered Jul 10 '15 at 15:43

Jashaszun

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Well dang, right after being marked as duplicate. Oops. – Jashaszun Jul 10 '15 at 15:43
Thanks, but please see my edited question. Do I have a some VS2013 problem? – haughtonomous Jul 10 '15 at 15:50
@NeilHaughton I think that your problem with referencing a unit test attribute should be another question entirely. It seems separate from this one. – Jashaszun Jul 10 '15 at 15:56
What I mean is that I can't compile .GetCustomAttributes(typeof(TestClassAttribute)....) unless I reference the dll in which it is defined, and VS2013 won't let me add it to the project. – haughtonomous Jul 10 '15 at 15:56
Ok, I shall raise another question if it can't be answered here. – haughtonomous Jul 10 '15 at 15:56
@NeilHaughton I understood what you meant the first time. I think that should be another question about referencing that unit test class when VS2013 won't let you. – Jashaszun Jul 10 '15 at 15:56
No worries, done. Comments are clearly crossing. – haughtonomous Jul 10 '15 at 16:07

How to use reflection to find certain classes in an assembly?

1 Answers1