Why does my .NET Attribute not perform an action?
attributes, c#, reflection
Solution
If you need to perform an action as control enters a method, you should look at aspect-oriented programming and frameworks such as PostSharp. Attributes are not designed to perform anything by themselves. They are just a bunch of data (or metadata if you will) attached to stuff in IL assemblies that can be queried at runtime.
Problem
I've created a simple Attribute: ``` [AttributeUsage(AttributeTargets.Method)] public class InitAttribute : System.Attribute { public InitAttribute() { Console.WriteLine("Works!"); } } ``` and I apply it to a simple method: ``` static class Logger { public static string _severity; public static void Init(string severity) { _severity = severity; } [Init()] public static void p() { Console.WriteLine(_severity); } } ``` What is going on is pretty straightforward. Only, I expect the attribute to perform an action (printing "Works!"), but this does not happen. Additionally, printing "Works!" is of course just for debugging purposes: I'd like to access the instance's property `_severity` (to check if is `!= null`, for example), but everything I keep reading about regarding attributes (that is pretty new to me) is about accessing the class' methods or properties and so on via reflection. Once I've evaluated `_severity`, how can I modify the behavior of the decorated method (in this case, raise an exception "Logger is not initialized" and do not execute it)? Any help appreciated.