CustomAttributeBuilder Class

Imports System.Threading
Imports System.Reflection
Imports System.Reflection.Emit

 _


' We will apply this custom attribute to our dynamic type.
Public Class ClassCreator

   Inherits Attribute

   Private creator As String

   Public ReadOnly Property GetCreator() As String
      Get
         Return creator
      End Get
   End Property


   Public Sub New(ByVal name As String)
      Me.creator = name
   End Sub 'New

End Class 'ClassCreator
 _ 

' We will apply this dynamic attribute to our dynamic method.
Public Class DateLastUpdated

   Inherits Attribute

   Private dateUpdated As String

   Public ReadOnly Property GetDateUpdated() As String
      Get
         Return dateUpdated
      End Get
   End Property


   Public Sub New(ByVal theDate As String)
      Me.dateUpdated = theDate
   End Sub 'New

End Class 'DateLastUpdated
 _ 

Class Example

   Public Shared Function BuildTypeWithCustomAttributesOnMethod() As Type

      Dim currentDomain As AppDomain = Thread.GetDomain()

      Dim myAsmName As New AssemblyName()
      myAsmName.Name = "MyAssembly"

      Dim myAsmBuilder As AssemblyBuilder = currentDomain.DefineDynamicAssembly(myAsmName, _
       AssemblyBuilderAccess.Run)

      Dim myModBuilder As ModuleBuilder = myAsmBuilder.DefineDynamicModule("MyModule")

      ' First, we'll build a type with a custom attribute attached.
      Dim myTypeBuilder As TypeBuilder = myModBuilder.DefineType("MyType", _
       TypeAttributes.Public)

      Dim ctorParams() As Type = {GetType(String)}
      Dim classCtorInfo As ConstructorInfo = GetType(ClassCreator).GetConstructor(ctorParams)

      Dim myCABuilder As New CustomAttributeBuilder(classCtorInfo, _
      New Object() {"Joe Programmer"})

      myTypeBuilder.SetCustomAttribute(myCABuilder)

      ' Now, let's build a method and add a custom attribute to it.
      Dim myMethodBuilder As MethodBuilder = myTypeBuilder.DefineMethod("HelloWorld", _
     MethodAttributes.Public, Nothing, New Type() {})

      ctorParams = New Type() {GetType(String)}
      classCtorInfo = GetType(DateLastUpdated).GetConstructor(ctorParams)

      Dim myCABuilder2 As New CustomAttributeBuilder(classCtorInfo, _
      New Object() {DateTime.Now.ToString()})

      myMethodBuilder.SetCustomAttribute(myCABuilder2)

      Dim myIL As ILGenerator = myMethodBuilder.GetILGenerator()

      myIL.EmitWriteLine("Hello, world!")
      myIL.Emit(OpCodes.Ret)

      Return myTypeBuilder.CreateType()

   End Function 'BuildTypeWithCustomAttributesOnMethod


   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)

      Dim myType As Type = BuildTypeWithCustomAttributesOnMethod()

      Dim myInstance As Object = Activator.CreateInstance(myType)

      Dim customAttrs As Object() = myType.GetCustomAttributes(True)

      outputBlock.Text &= "Custom Attributes for Type 'MyType':" & vbCrLf

      Dim attrVal As Object = Nothing

      Dim customAttr As Object
      For Each customAttr In customAttrs
         attrVal = GetType(ClassCreator).InvokeMember("GetCreator", _
      BindingFlags.GetProperty, _
      Nothing, customAttr, New Object() {})
         outputBlock.Text &= String.Format("-- Attribute: [{0} = ""{1}""]", customAttr, attrVal) & vbCrLf
      Next customAttr

      outputBlock.Text &= "Custom Attributes for Method 'HelloWorld()' in 'MyType':" & vbCrLf

      customAttrs = myType.GetMember("HelloWorld")(0).GetCustomAttributes(True)

      For Each customAttr In customAttrs
         attrVal = GetType(DateLastUpdated).InvokeMember("GetDateUpdated", _
      BindingFlags.GetProperty, _
      Nothing, customAttr, New Object() {})
         outputBlock.Text &= String.Format("-- Attribute: [{0} = ""{1}""]", customAttr, attrVal) & vbCrLf
      Next customAttr

      outputBlock.Text &= "---" & vbCrLf

      outputBlock.Text &= myType.InvokeMember("HelloWorld", BindingFlags.InvokeMethod, _
      Nothing, myInstance, New Object() {}) & vbCrLf
   End Sub 'Main

End Class 'MethodBuilderCustomAttributesDemo

using System;
using System.Threading;
using System.Reflection;
using System.Reflection.Emit;


// We will apply this custom attribute to our dynamic type.
public class ClassCreator : Attribute
{
   private string creator;
   public string Creator
   {
      get
      {
         return creator;
      }
   }

   public ClassCreator(string name)
   {
      this.creator = name;
   }

}

// We will apply this dynamic attribute to our dynamic method.
public class DateLastUpdated : Attribute
{
   private string dateUpdated;
   public string DateUpdated
   {
      get
      {
         return dateUpdated;
      }
   }

   public DateLastUpdated(string theDate)
   {
      this.dateUpdated = theDate;
   }

}

class Example
{

   public static Type BuildTypeWithCustomAttributesOnMethod()
   {

      AppDomain currentDomain = Thread.GetDomain();

      AssemblyName myAsmName = new AssemblyName();
      myAsmName.Name = "MyAssembly";

      AssemblyBuilder myAsmBuilder = currentDomain.DefineDynamicAssembly(
                      myAsmName, AssemblyBuilderAccess.Run);

      ModuleBuilder myModBuilder = myAsmBuilder.DefineDynamicModule("MyModule");

      // First, we'll build a type with a custom attribute attached.

      TypeBuilder myTypeBuilder = myModBuilder.DefineType("MyType",
                     TypeAttributes.Public);

      Type[] ctorParams = new Type[] { typeof(string) };
      ConstructorInfo classCtorInfo = typeof(ClassCreator).GetConstructor(ctorParams);

      CustomAttributeBuilder myCABuilder = new CustomAttributeBuilder(
                     classCtorInfo,
                     new object[] { "Joe Programmer" });

      myTypeBuilder.SetCustomAttribute(myCABuilder);

      // Now, let's build a method and add a custom attribute to it.

      MethodBuilder myMethodBuilder = myTypeBuilder.DefineMethod("HelloWorld",
                  MethodAttributes.Public,
                  null,
                  new Type[] { });

      ctorParams = new Type[] { typeof(string) };
      classCtorInfo = typeof(DateLastUpdated).GetConstructor(ctorParams);

      CustomAttributeBuilder myCABuilder2 = new CustomAttributeBuilder(
                     classCtorInfo,
                     new object[] { DateTime.Now.ToString() });

      myMethodBuilder.SetCustomAttribute(myCABuilder2);

      ILGenerator myIL = myMethodBuilder.GetILGenerator();

      myIL.EmitWriteLine("Hello, world!");
      myIL.Emit(OpCodes.Ret);

      return myTypeBuilder.CreateType();

   }

   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {

      Type myType = BuildTypeWithCustomAttributesOnMethod();

      object myInstance = Activator.CreateInstance(myType);

      object[] customAttrs = myType.GetCustomAttributes(true);

      outputBlock.Text += "Custom Attributes for Type 'MyType':" + "\n";

      object attrVal = null;

      foreach (object customAttr in customAttrs)
      {
         attrVal = typeof(ClassCreator).InvokeMember("Creator",
                    BindingFlags.GetProperty,
                    null, customAttr, new object[] { });
         outputBlock.Text += String.Format("-- Attribute: [{0} = \"{1}\"]", customAttr, attrVal) + "\n";
      }

      outputBlock.Text += "Custom Attributes for Method 'HelloWorld()' in 'MyType':" + "\n";

      customAttrs = myType.GetMember("HelloWorld")[0].GetCustomAttributes(true);

      foreach (object customAttr in customAttrs)
      {
         attrVal = typeof(DateLastUpdated).InvokeMember("DateUpdated",
                    BindingFlags.GetProperty,
                    null, customAttr, new object[] { });
         outputBlock.Text += String.Format("-- Attribute: [{0} = \"{1}\"]", customAttr, attrVal) + "\n";
      }

      outputBlock.Text += "---" + "\n";

      outputBlock.Text += myType.InvokeMember("HelloWorld",
              BindingFlags.InvokeMethod,
              null, myInstance, new object[] { }) + "\n";


   }

}