CustomAttributeBuilder Class

Represents a custom attribute in a form that can be attached to a type or member that is being emitted.

Inheritance Hierarchy

System.Object
  System.Reflection.Emit.CustomAttributeBuilder

Namespace:  System.Reflection.Emit
Assembly:  mscorlib (in mscorlib.dll)

Syntax

'Declaration
<ClassInterfaceAttribute(ClassInterfaceType.None)> _
<ComVisibleAttribute(True)> _
Public Class CustomAttributeBuilder
[ClassInterfaceAttribute(ClassInterfaceType.None)]
[ComVisibleAttribute(true)]
public class CustomAttributeBuilder

The CustomAttributeBuilder type exposes the following members.

Constructors

  Name Description
Public method CustomAttributeBuilder(ConstructorInfo, array<Object[]) Initializes a new instance of the CustomAttributeBuilder class given the constructor for the custom attribute and the arguments to the constructor.
Public method CustomAttributeBuilder(ConstructorInfo, array<Object[], array<FieldInfo[], array<Object[]) Initializes a new instance of the CustomAttributeBuilder class, given the constructor for the custom attribute, the arguments to the constructor, and a set of named field/value pairs.
Public method CustomAttributeBuilder(ConstructorInfo, array<Object[], array<PropertyInfo[], array<Object[]) Initializes a new instance of the CustomAttributeBuilder class, given the constructor for the custom attribute, the arguments to the constructor, and a set of named property or value pairs.
Public method CustomAttributeBuilder(ConstructorInfo, array<Object[], array<PropertyInfo[], array<Object[], array<FieldInfo[], array<Object[]) Initializes a new instance of the CustomAttributeBuilder class, given the constructor for the custom attribute, the arguments to the constructor, a set of named property or value pairs, and a set of named field or value pairs.

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Methods

  Name Description
Public method Equals(Object) Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected method Finalize Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
Public method GetHashCode Serves as a hash function for a particular type. (Inherited from Object.)
Public method GetType Gets the Type of the current instance. (Inherited from Object.)
Protected method MemberwiseClone Creates a shallow copy of the current Object. (Inherited from Object.)
Public method ToString Returns a string that represents the current object. (Inherited from Object.)

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Remarks

Use the CustomAttributeBuilder object returned by the constructor to attach a custom attribute to a dynamic type or member. Associate the custom attribute with a builder instance by calling the SetCustomAttribute method on that builder instance. For example, create a CustomAttributeBuilder to describe an instance of AssemblyCultureAttribute by supplying the constructor of AssemblyCultureAttribute and its argument. Then call the AssemblyBuilder.SetCustomAttribute method to attach the AssemblyCultureAttribute to a dynamic assembly.

Examples

The following code example illustrates the use of CustomAttributeBuilder.


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";


   }

}

Version Information

Silverlight

Supported in: 5, 4, 3

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.