Find generic type over reflection

Question

I have a small snipped of code, which checks, wehter an class exists or not.

At first i load all available types:

List<Type> types = new List<Type>(); foreach (Assembly asm in AppDomain.CurrentDomain.GetAssemblies()) { try { types.AddRange(asm.GetTypes()); } catch (ReflectionTypeLoadException e) { types.AddRange(e.Types.Where(t => t != null)); } }

Than i concat namespace and class name (which should be checked):

string fullName = ns.Trim() + "." + classToProof.Trim();

And in the and, i check wether the class exists:

int found = types.Where(innerItem => innerItem.FullName == fullName).ToList().Count;

But i have the problem, that if i check generic classes, for example System.Collections.Generic.Dictionary, found is always 0 (should be 1).

Does anyone has an idea, why this happens?

Solution:

List<string> types = new List<string>(); foreach (Assembly asm in AppDomain.CurrentDomain.GetAssemblies()) { try { types.AddRange(asm.GetTypes().Select(item => (!item.FullName.Contains("`") ? item.FullName : item.FullName.Substring(0, item.FullName.IndexOf("`"))))); } catch (ReflectionTypeLoadException e) { types.AddRange(e.Types.Where(t => t != null).Select(item => (!item.FullName.Contains("`") ? item.FullName : item.FullName.Substring(0, item.FullName.IndexOf("`"))))); } }

I removed all ` from the full name, and fill a prepared list of strings.

Thank you

@MurrayFoxcroft This is absolutely wrong.

Matías Fidemraizer
– Matías Fidemraizer

2015-01-09 13:10:36 +00:00
Commented Jan 9, 2015 at 13:10 — Matías Fidemraizer
– Matías Fidemraizer, Commented Jan 9, 2015 at 13:10

Selman Genç · Accepted Answer · 2015-01-09 13:39:39Z

It's probably because generic uses `` with a number that indicates the generic argument count like List`1. And your type name does not have it. To prevent this I would suggest checking the type directly instead of name:

 types.Where(t => t == typeof(Dictionary<,>))

Or you can use Substring and IndexOf to get the part before ``

int found = types .Where(t => t.IsGenericType ? t.FullName.Substring(0,t.FullName.IndexOf('`')) == fullName : t.FullName == fullName).ToList().Count;

Gergely Hamos · Accepted Answer · 2015-11-17 15:53:57Z

Sorry, but Matias is right, your solution is technically wrong.

The main problem is, that in a namespace types with the same name but with different type args can coexists at the same time. So this is valid:

SomeNameSpace { public class MyType {} // FullName: SomeNameSpace.MyType public class MyType<T> {} // FullName: SomeNameSpace.MyType`1 }

So, when you try to find System.Collections.Generic.Dictionary, you are actually trying to find a class with name "System.Collections.Generic.Dictionary" but with 0 type arguments. There is no such type in System.Collections.Generic.

If you want to find System.Collections.Generic.Dictionary, that's OK, but the full name of that type is "System.Collections.Generic.Dictionary`2", where the backtick followed by the number 2 means that you talk about a generic type with 2 type args.

Your solution may works, and may solves your concrete problem, but you have to understand that it is technically wrong, because if you removes the backtick-part of the generic typenames, then you actually merges all generic versions of a type into one name. So be aware, and consider using your original code (which is OK), and the correct name of the generic types.

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