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CustomAttributeBuilder Class

Helps build custom attributes.

For a list of all members of this type, see CustomAttributeBuilder Members.

System.Object
   System.Reflection.Emit.CustomAttributeBuilder

[Visual Basic]
Public Class CustomAttributeBuilder
[C#]
public class CustomAttributeBuilder
[C++]
public __gc class CustomAttributeBuilder
[JScript]
public class CustomAttributeBuilder

Thread Safety

Reflection Emit is thread-safe when using assemblies that were created with the AppDomain.DefineDynamicAssembly method with the Boolean parameter isSynchronized set to true.

Remarks

Use the CustomAttributeBuilder object returned by the constructor to describe the custom attribute. Associate the CustomAttribute to 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.

Example

[Visual Basic, C#, C++] 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[] { }));
                           
    
   }

}


[C++] 
#using <mscorlib.dll>

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 __gc class ClassCreator : public Attribute {
private:
   String*  creator;
public:
   __property String* get_Creator() {
      return creator;
   }


public:
   ClassCreator(String* name) {
      this->creator = name;
   }
};

// We will apply this dynamic attribute to our dynamic method.
public __gc class DateLastUpdated : public Attribute {
private:
   String*  dateUpdated;
public:
   __property String* get_DateUpdated() {
      return dateUpdated;
   }
public:
   DateLastUpdated(String* theDate) {
      this->dateUpdated = theDate;
   }
};

Type* BuildTypeWithCustomAttributesOnMethod() {

   AppDomain*  currentDomain = Thread::GetDomain();

   AssemblyName* myAsmName = new AssemblyName();
   myAsmName->Name = S"MyAssembly";

   AssemblyBuilder*  myAsmBuilder = currentDomain->DefineDynamicAssembly(myAsmName, AssemblyBuilderAccess::Run);

   ModuleBuilder*  myModBuilder = myAsmBuilder->DefineDynamicModule(S"MyModule");

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

   TypeBuilder*  myTypeBuilder = myModBuilder->DefineType(S"MyType",
      TypeAttributes::Public);

   Type* temp6 [] = {__typeof(String)};
   Type* ctorParams[] = temp6;
   ConstructorInfo*  classCtorInfo = __typeof(ClassCreator)->GetConstructor(ctorParams);

   Object* temp0 [] = {S"Joe Programmer"};
   CustomAttributeBuilder* myCABuilder = new CustomAttributeBuilder(classCtorInfo, temp0);

   myTypeBuilder->SetCustomAttribute(myCABuilder);

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

   Type* temp1 [] = new Type*[0];
   MethodBuilder*  myMethodBuilder = myTypeBuilder->DefineMethod(S"HelloWorld",
      MethodAttributes::Public,
      0,
      temp1);

   Type* temp7 [] = {__typeof(String)};
   ctorParams = temp7;
   classCtorInfo = __typeof(DateLastUpdated)->GetConstructor(ctorParams);

   Object* temp2 [] = {DateTime::Now.ToString()};
   CustomAttributeBuilder* myCABuilder2 = new CustomAttributeBuilder(classCtorInfo, temp2);

   myMethodBuilder->SetCustomAttribute(myCABuilder2);

   ILGenerator*  myIL = myMethodBuilder->GetILGenerator();

   myIL->EmitWriteLine(S"Hello, world!");
   myIL->Emit(OpCodes::Ret);

   return myTypeBuilder->CreateType();
}

int main() {

   Type*  myType = BuildTypeWithCustomAttributesOnMethod();

   Object* myInstance = Activator::CreateInstance(myType);

   Object* customAttrs[] = myType->GetCustomAttributes(true);

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

   Object* attrVal = 0;

   System::Collections::IEnumerator* myEnum = customAttrs->GetEnumerator();
   while (myEnum->MoveNext()) {
      Object* customAttr = __try_cast<Object*>(myEnum->Current);

      Object* temp3 [] = new Object*[0];
      attrVal = __typeof(ClassCreator)->InvokeMember(S"Creator",
         BindingFlags::GetProperty,
         0, customAttr, temp3);
      Console::WriteLine(S"-- Attribute: [{0} = \"{1}\"]", customAttr, attrVal);
   }

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

   customAttrs = myType->GetMember(S"HelloWorld")[0]->GetCustomAttributes(true);

   System::Collections::IEnumerator* myEnum2 = customAttrs->GetEnumerator();
   while (myEnum2->MoveNext()) {
      Object* customAttr = __try_cast<Object*>(myEnum2->Current);
      Object* temp4 [] = new Object*[0];
      attrVal = __typeof(DateLastUpdated)->InvokeMember(S"DateUpdated",
         BindingFlags::GetProperty,
         0, customAttr, temp4);
      Console::WriteLine(S"-- Attribute: [{0} = \"{1}\"]", customAttr, attrVal);
   }

   Console::WriteLine(S"---");

   Object* temp5 [] = new Object*[0];
   Console::WriteLine(myType->InvokeMember(S"HelloWorld",
      BindingFlags::InvokeMethod,
      0, myInstance, temp5));
}

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Namespace: System.Reflection.Emit

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

Assembly: Mscorlib (in Mscorlib.dll)

See Also

CustomAttributeBuilder Members | System.Reflection.Emit Namespace

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