Attribute Class

Imports System.Reflection

' An enumeration of animals. Start at 1 (0 = uninitialized).
Public Enum Animal
   ' Pets
   Dog = 1
   Cat
   Bird
End Enum

' Visual Basic requires the AttributeUsage be specified.
' A custom attribute to allow a target to have a pet.
<AttributeUsage(AttributeTargets.Method)> _
Public Class AnimalTypeAttribute
   Inherits Attribute

   ' The constructor is called when the attribute is set.
   Public Sub New(ByVal animal As Animal)
      Me.thePet = animal
   End Sub

   ' Keep a variable internally ...
   Protected thePet As Animal

   ' .. and show a copy to the outside world.
   Public Property Pet() As Animal
      Get
         Return thePet
      End Get
      Set(ByVal Value As Animal)
         thePet = Value
      End Set
   End Property
End Class

Class AnimalTypeTestClass
   <AnimalType(Animal.Dog)> _
   Public Sub DogMethod()
   End Sub

   <AnimalType(Animal.Cat)> _
   Public Sub CatMethod()
   End Sub

   <AnimalType(Animal.Bird)> _
   Public Sub BirdMethod()
   End Sub
End Class

Module Example
   Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      Dim testClass As New AnimalTypeTestClass()
      Dim tcType As Type = testClass.GetType()
      Dim mInfo As MethodInfo
      ' Iterate through all the methods of the class.
      For Each mInfo In tcType.GetMethods()
         Dim attr As Attribute
         ' Iterate through all the attributes of the method.
         For Each attr In Attribute.GetCustomAttributes(mInfo)
            If TypeOf attr Is AnimalTypeAttribute Then
               Dim attrCustom As AnimalTypeAttribute = _
                   CType(attr, AnimalTypeAttribute)
               outputBlock.Text += String.Format("Method {0} has a pet {1} attribute.", _
                    mInfo.Name(), attrCustom.Pet.ToString()) + vbCrLf
            End If
         Next
      Next
   End Sub
End Module

' Output:
' Method DogMethod has a pet Dog attribute.
' Method CatMethod has a pet Cat attribute.
' Method BirdMethod has a pet Bird attribute.

using System;
using System.Reflection;

// An enumeration of animals. Start at 1 (0 = uninitialized).
public enum Animal
{
   // Pets.
   Dog = 1,
   Cat,
   Bird,
}

// A custom attribute to allow a target to have a pet.
public class AnimalTypeAttribute : Attribute
{
   // The constructor is called when the attribute is set.
   public AnimalTypeAttribute(Animal pet)
   {
      thePet = pet;
   }

   // Keep a variable internally ...
   protected Animal thePet;

   // .. and show a copy to the outside world.
   public Animal Pet
   {
      get { return thePet; }
      set { thePet = Pet; }
   }
}

// A test class where each method has its own pet.
class AnimalTypeTestClass
{
   [AnimalType(Animal.Dog)]
   public void DogMethod() { }

   [AnimalType(Animal.Cat)]
   public void CatMethod() { }

   [AnimalType(Animal.Bird)]
   public void BirdMethod() { }
}

class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      AnimalTypeTestClass testClass = new AnimalTypeTestClass();
      Type type = testClass.GetType();
      // Iterate through all the methods of the class.
      foreach (MethodInfo mInfo in type.GetMethods())
      {
         // Iterate through all the Attributes for each method.
         foreach (Attribute attr in
             Attribute.GetCustomAttributes(mInfo))
         {
            // Check for the AnimalType attribute.
            if (attr.GetType() == typeof(AnimalTypeAttribute))
               outputBlock.Text += String.Format(
                   "Method {0} has a pet {1} attribute.",
                   mInfo.Name, ((AnimalTypeAttribute)attr).Pet) + "\n";
         }

      }
   }
}
/*
 * Output:
 * Method DogMethod has a pet Dog attribute.
 * Method CatMethod has a pet Cat attribute.
 * Method BirdMethod has a pet Bird attribute.
 */