Csharp/C Sharp by API/System/AttributeUsage

AttributeUsage(AttributeTargets)

<source lang="csharp"> using System; [AttributeUsage(AttributeTargets.Class)] public class RandomSupplier : Attribute {

 public RandomSupplier()
 {
 }

} [AttributeUsage(AttributeTargets.Method )] public class RandomMethod : Attribute {

 public RandomMethod()
 {
 }

} [RandomSupplier] public class OriginalRandom {

 [RandomMethod]
 public int GetRandom()
 {
   return 5;
 }

} using System; [RandomSupplier] public class NewRandom {

 [RandomMethod]
 public int ImprovedRandom()
 {
   Random r = new Random();
   return r.Next(1, 100);
 }

} public class AnotherClass {

 public int NotRandom()
 {
   return 1;
 }

} using System; using System.Reflection; class MainClass {

 public static void Main(string[] args) 
 {
   RandomSupplier rs;
   RandomMethod rm;
   foreach(string s in args)
   {
     Assembly a = Assembly.LoadFrom(s);
     foreach(Type t in a.GetTypes())
     {
       rs = (RandomSupplier) Attribute.GetCustomAttribute(
        t, typeof(RandomSupplier));
       if(rs != null)
       {
         Console.WriteLine("Found RandomSupplier class {0} in {1}",
          t, s);
         foreach(MethodInfo m in t.GetMethods())
         {
           rm = (RandomMethod) Attribute.GetCustomAttribute(
            m, typeof(RandomMethod));
           if(rm != null)
           {
             Console.WriteLine("Found RandomMethod method {0}"
              , m.Name );
           }
         }        
       }
     }
   }
 }

}

</source>