using System;

[AttributeUsage(AttributeTargets.Class|
                AttributeTargets.Struct,
                AllowMultiple=true)]
public class Author : Attribute
{
   string authorName;
   public double verSion;

   public Author(string name) 
   {
      authorName = name;
      verSion = 1.0; 
   }

   public string getName() 
   {
      return authorName; 
   }
}

[Author("Some Author")]
class FirstClass 
{
   /*...*/ 
}

class SecondClass  // no Author attribute
{
   /*...*/ 
}

[Author("Some Author"), 
       Author("Some Other Author", verSion=1.1)]
class ThirdClass 
{ 
   /*...*/ 
}

class AuthorInfo 
{
   public static void Main() 
   {
      PrintAuthorInfo(typeof(FirstClass));
      PrintAuthorInfo(typeof(SecondClass));
      PrintAuthorInfo(typeof(ThirdClass));
   }
   public static void PrintAuthorInfo(Type type) 
   {
      Console.WriteLine("Author information for {0}",
                        type);
      Attribute[] attributeArray =
          Attribute.GetCustomAttributes(type);
      foreach(Attribute attrib in attributeArray) 
      {
         if (attrib is Author) 
         {
            Author author = (Author)attrib;
            Console.WriteLine("   {0}, version {1:f}",
                              author.getName(),
                              author.verSion);
         }
      }
      Console.WriteLine();
   }
}