.NET Framework Class Library
CustomAttributeBuilder Class

Helps build custom attributes.

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

Visual Basic (Declaration)
<ComVisibleAttribute(True)> _
<ClassInterfaceAttribute(ClassInterfaceType.None)> _
<HostProtectionAttribute(SecurityAction.LinkDemand, MayLeakOnAbort := True)> _
Public Class CustomAttributeBuilder _
    Implements _CustomAttributeBuilder
Visual Basic (Usage)
Dim instance As CustomAttributeBuilder
C#
[ComVisibleAttribute(true)]
[ClassInterfaceAttribute(ClassInterfaceType.None)]
[HostProtectionAttribute(SecurityAction.LinkDemand, MayLeakOnAbort = true)]
public class CustomAttributeBuilder : _CustomAttributeBuilder
Visual C++
[ComVisibleAttribute(true)]
[ClassInterfaceAttribute(ClassInterfaceType::None)]
[HostProtectionAttribute(SecurityAction::LinkDemand, MayLeakOnAbort = true)]
public ref class CustomAttributeBuilder : _CustomAttributeBuilder
JScript
public class CustomAttributeBuilder implements _CustomAttributeBuilder
Remarks

NoteNote:

The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: MayLeakOnAbort. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes.

Use the CustomAttributeBuilder object returned by the constructor to describe the custom attribute. Associate the CustomAttribute 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 SetCustomAttribute on an AssemblyBuilder to establish the association.

Examples

The following code sample illustrates the use of CustomAttributeBuilder.

Visual Basic
Imports System
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(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(theDate As String)
      Me.dateUpdated = theDate
   End Sub 'New

End Class 'DateLastUpdated
 _ 

Class MethodBuilderCustomAttributesDemo

   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 Main()

      Dim myType As Type = BuildTypeWithCustomAttributesOnMethod()

      Dim myInstance As Object = Activator.CreateInstance(myType)

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

      Console.WriteLine("Custom Attributes for Type 'MyType':")

      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() {})
         Console.WriteLine("-- Attribute: [{0} = ""{1}""]", customAttr, attrVal)
      Next customAttr

      Console.WriteLine("Custom Attributes for Method 'HelloWorld()' in 'MyType':")

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

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

      Console.WriteLine("---")

      Console.WriteLine(myType.InvokeMember("HelloWorld", BindingFlags.InvokeMethod, _
                        Nothing, myInstance, New Object() {}))
   End Sub 'Main

End Class 'MethodBuilderCustomAttributesDemo

C#
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 MethodBuilderCustomAttributesDemo

{

   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 Main() 
   {

    Type myType = BuildTypeWithCustomAttributesOnMethod();

    object myInstance = Activator.CreateInstance(myType);

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

    Console.WriteLine("Custom Attributes for Type 'MyType':");

    object attrVal = null;

    foreach (object customAttr in customAttrs) 
       {
       attrVal = typeof(ClassCreator).InvokeMember("Creator", 
                      BindingFlags.GetProperty,
                      null, customAttr, new object[] { });
       Console.WriteLine("-- Attribute: [{0} = \"{1}\"]", customAttr, attrVal);
        }

    Console.WriteLine("Custom Attributes for Method 'HelloWorld()' in 'MyType':");

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

    foreach (object customAttr in customAttrs) 
       {
       attrVal = typeof(DateLastUpdated).InvokeMember("DateUpdated", 
                      BindingFlags.GetProperty,
                      null, customAttr, new object[] { });
       Console.WriteLine("-- Attribute: [{0} = \"{1}\"]", customAttr, attrVal);
        }

    Console.WriteLine("---");

    Console.WriteLine(myType.InvokeMember("HelloWorld",
              BindingFlags.InvokeMethod,
              null, myInstance, new object[] { }));
                           
    
   }

}

Visual C++
using namespace System;
using namespace System::Threading;
using namespace System::Reflection;
using namespace System::Reflection::Emit;

// We will apply this custom attribute to our dynamic type.
public ref class ClassCreator: public Attribute
{
private:
   String^ creator;

public:

   property String^ Creator 
   {
      String^ get()
      {
         return creator;
      }

   }
   ClassCreator( String^ name )
   {
      this->creator = name;
   }

};


// We will apply this dynamic attribute to our dynamic method.
public ref class DateLastUpdated: public Attribute
{
private:
   String^ dateUpdated;

public:

   property String^ DateUpdated 
   {
      String^ get()
      {
         return dateUpdated;
      }

   }
   DateLastUpdated( String^ theDate )
   {
      this->dateUpdated = theDate;
   }

};

Type^ BuildTypeWithCustomAttributesOnMethod()
{
   AppDomain^ currentDomain = Thread::GetDomain();
   AssemblyName^ myAsmName = gcnew 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 );
   array<Type^>^temp6 = {String::typeid};
   array<Type^>^ctorParams = temp6;
   ConstructorInfo^ classCtorInfo = ClassCreator::typeid->GetConstructor( ctorParams );
   array<Object^>^temp0 = {"Joe Programmer"};
   CustomAttributeBuilder^ myCABuilder = gcnew CustomAttributeBuilder( classCtorInfo,temp0 );
   myTypeBuilder->SetCustomAttribute( myCABuilder );

   // Now, let's build a method and add a custom attribute to it.
   array<Type^>^temp1 = gcnew array<Type^>(0);
   MethodBuilder^ myMethodBuilder = myTypeBuilder->DefineMethod( "HelloWorld", MethodAttributes::Public, nullptr, temp1 );
   array<Type^>^temp7 = {String::typeid};
   ctorParams = temp7;
   classCtorInfo = DateLastUpdated::typeid->GetConstructor( ctorParams );
   array<Object^>^temp2 = {DateTime::Now.ToString()};
   CustomAttributeBuilder^ myCABuilder2 = gcnew CustomAttributeBuilder( classCtorInfo,temp2 );
   myMethodBuilder->SetCustomAttribute( myCABuilder2 );
   ILGenerator^ myIL = myMethodBuilder->GetILGenerator();
   myIL->EmitWriteLine( "Hello, world!" );
   myIL->Emit( OpCodes::Ret );
   return myTypeBuilder->CreateType();
}

int main()
{
   Type^ myType = BuildTypeWithCustomAttributesOnMethod();
   Object^ myInstance = Activator::CreateInstance( myType );
   array<Object^>^customAttrs = myType->GetCustomAttributes( true );
   Console::WriteLine( "Custom Attributes for Type 'MyType':" );
   Object^ attrVal = nullptr;
   System::Collections::IEnumerator^ myEnum = customAttrs->GetEnumerator();
   while ( myEnum->MoveNext() )
   {
      Object^ customAttr = safe_cast<Object^>(myEnum->Current);
      array<Object^>^temp3 = gcnew array<Object^>(0);
      attrVal = ClassCreator::typeid->InvokeMember( "Creator", BindingFlags::GetProperty, nullptr, customAttr, temp3 );
      Console::WriteLine( "-- Attribute: [{0} = \"{1}\"]", customAttr, attrVal );
   }

   Console::WriteLine( "Custom Attributes for Method 'HelloWorld()' in 'MyType':" );
   customAttrs = myType->GetMember( "HelloWorld" )[ 0 ]->GetCustomAttributes( true );
   System::Collections::IEnumerator^ myEnum2 = customAttrs->GetEnumerator();
   while ( myEnum2->MoveNext() )
   {
      Object^ customAttr = safe_cast<Object^>(myEnum2->Current);
      array<Object^>^temp4 = gcnew array<Object^>(0);
      attrVal = DateLastUpdated::typeid->InvokeMember( "DateUpdated", BindingFlags::GetProperty, nullptr, customAttr, temp4 );
      Console::WriteLine( "-- Attribute: [{0} = \"{1}\"]", customAttr, attrVal );
   }

   Console::WriteLine( "---" );
   array<Object^>^temp5 = gcnew array<Object^>(0);
   Console::WriteLine( myType->InvokeMember( "HelloWorld", BindingFlags::InvokeMethod, nullptr, myInstance, temp5 ) );
}
Inheritance Hierarchy

System..::.Object
  System.Reflection.Emit..::.CustomAttributeBuilder
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.
Platforms

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
Version Information

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0
See Also

Reference

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