FieldBuilder Class

Definition

Defines and represents a field. This class cannot be inherited.

[System.Runtime.InteropServices.ClassInterface(System.Runtime.InteropServices.ClassInterfaceType.None)]
[System.Runtime.InteropServices.ComVisible(true)]
public sealed class FieldBuilder : System.Reflection.FieldInfo, System.Runtime.InteropServices._FieldBuilder
Inheritance
Attributes
Implements

Inherited Members

System.Object

System.Reflection.FieldInfo

System.Reflection.MemberInfo

Examples

The following code sample illustrates the use of FieldBuilder.

using namespace System;
using namespace System::Threading;
using namespace System::Reflection;
using namespace System::Reflection::Emit;
Type^ CreateType( AppDomain^ currentDomain )
{
   // Create an assembly.
   AssemblyName^ myAssemblyName = gcnew AssemblyName;
   myAssemblyName->Name = "DynamicAssembly";
   AssemblyBuilder^ myAssembly = currentDomain->DefineDynamicAssembly( myAssemblyName, AssemblyBuilderAccess::Run );

   // Create a dynamic module in Dynamic Assembly.
   ModuleBuilder^ myModuleBuilder = myAssembly->DefineDynamicModule( "MyModule" );

   // Define a public class named S"MyClass" in the assembly.
   TypeBuilder^ myTypeBuilder = myModuleBuilder->DefineType( "MyClass", TypeAttributes::Public );

   // Define a private String field named S"MyField" in the type.
   FieldBuilder^ myFieldBuilder = myTypeBuilder->DefineField( "MyField", String::typeid, static_cast<FieldAttributes>(FieldAttributes::Private | FieldAttributes::Static) );

   // Create the constructor.
   array<Type^>^constructorArgs = {String::typeid};
   ConstructorBuilder^ constructor = myTypeBuilder->DefineConstructor( MethodAttributes::Public, CallingConventions::Standard, constructorArgs );
   ILGenerator^ constructorIL = constructor->GetILGenerator();
   constructorIL->Emit( OpCodes::Ldarg_0 );
   ConstructorInfo^ superConstructor = Object::typeid->GetConstructor( gcnew array<Type^>(0) );
   constructorIL->Emit( OpCodes::Call, superConstructor );
   constructorIL->Emit( OpCodes::Ldarg_0 );
   constructorIL->Emit( OpCodes::Ldarg_1 );
   constructorIL->Emit( OpCodes::Stfld, myFieldBuilder );
   constructorIL->Emit( OpCodes::Ret );

   // Create the MyMethod method.
   MethodBuilder^ myMethodBuilder = myTypeBuilder->DefineMethod( "MyMethod", MethodAttributes::Public, String::typeid, nullptr );
   ILGenerator^ methodIL = myMethodBuilder->GetILGenerator();
   methodIL->Emit( OpCodes::Ldarg_0 );
   methodIL->Emit( OpCodes::Ldfld, myFieldBuilder );
   methodIL->Emit( OpCodes::Ret );
   Console::WriteLine( "Name               : {0}", myFieldBuilder->Name );
   Console::WriteLine( "DeclaringType      : {0}", myFieldBuilder->DeclaringType );
   Console::WriteLine( "Type               : {0}", myFieldBuilder->FieldType );
   Console::WriteLine( "Token              : {0}", myFieldBuilder->GetToken().Token );
   return myTypeBuilder->CreateType();
}

int main()
{
   try
   {
      Type^ myType = CreateType( Thread::GetDomain() );

      // Create an instance of the S"HelloWorld" class.
      array<Object^>^type = {"HelloWorld"};
      Object^ helloWorld = Activator::CreateInstance( myType, type );

      // Invoke the S"MyMethod" method of the S"MyClass" class.
      Object^ myObject = myType->InvokeMember( "MyMethod", BindingFlags::InvokeMethod, nullptr, helloWorld, nullptr );
      Console::WriteLine( "MyClass::MyMethod returned: \"{0}\"", myObject );
   }
   catch ( Exception^ e ) 
   {
      Console::WriteLine( "Exception Caught {0}", e->Message );
   }
}
using System;
using System.Threading;
using System.Reflection;
using System.Reflection.Emit;
using System.Security.Permissions;

public class FieldBuilder_Sample
{
   private static Type CreateType(AppDomain currentDomain)
   {

      // Create an assembly.
      AssemblyName myAssemblyName = new AssemblyName();
      myAssemblyName.Name = "DynamicAssembly";
      AssemblyBuilder myAssembly =
                     currentDomain.DefineDynamicAssembly(myAssemblyName,AssemblyBuilderAccess.Run);
      // Create a dynamic module in Dynamic Assembly.
      ModuleBuilder myModuleBuilder=myAssembly.DefineDynamicModule("MyModule");
      // Define a public class named "MyClass" in the assembly.
      TypeBuilder myTypeBuilder= myModuleBuilder.DefineType("MyClass",TypeAttributes.Public);

      // Define a private String field named "MyField" in the type.
      FieldBuilder myFieldBuilder= myTypeBuilder.DefineField("MyField",
          typeof(string),FieldAttributes.Private|FieldAttributes.Static);
      // Create the constructor.
      Type[] constructorArgs = { typeof(String) };
      ConstructorBuilder constructor = myTypeBuilder.DefineConstructor(
         MethodAttributes.Public, CallingConventions.Standard, constructorArgs);
      ILGenerator constructorIL = constructor.GetILGenerator();
      constructorIL.Emit(OpCodes.Ldarg_0);
      ConstructorInfo superConstructor = typeof(Object).GetConstructor(new Type[0]);
      constructorIL.Emit(OpCodes.Call, superConstructor);
      constructorIL.Emit(OpCodes.Ldarg_0);
      constructorIL.Emit(OpCodes.Ldarg_1);
      constructorIL.Emit(OpCodes.Stfld, myFieldBuilder);
      constructorIL.Emit(OpCodes.Ret);

      // Create the MyMethod method.
      MethodBuilder myMethodBuilder= myTypeBuilder.DefineMethod("MyMethod",
                           MethodAttributes.Public,typeof(String),null);
      ILGenerator methodIL = myMethodBuilder.GetILGenerator();
      methodIL.Emit(OpCodes.Ldarg_0);
      methodIL.Emit(OpCodes.Ldfld, myFieldBuilder);
      methodIL.Emit(OpCodes.Ret);
      Console.WriteLine("Name               :"+myFieldBuilder.Name);
      Console.WriteLine("DeclaringType      :"+myFieldBuilder.DeclaringType);
      Console.WriteLine("Type               :"+myFieldBuilder.FieldType);
      Console.WriteLine("Token              :"+myFieldBuilder.GetToken().Token);
      return myTypeBuilder.CreateType();
   }

   [PermissionSetAttribute(SecurityAction.Demand, Name="FullTrust")]
   public static void Main()
   {
      try
      {
         Type myType = CreateType(Thread.GetDomain());
         // Create an instance of the "HelloWorld" class.
         Object helloWorld = Activator.CreateInstance(myType, new Object[] { "HelloWorld" });
         // Invoke the "MyMethod" method of the "MyClass" class.
         Object myObject  = myType.InvokeMember("MyMethod",
                        BindingFlags.InvokeMethod, null, helloWorld, null);
         Console.WriteLine("MyClass.MyMethod returned: \"" + myObject + "\"");
      }
      catch( Exception e)
      {
         Console.WriteLine("Exception Caught "+e.Message);
      }
  }
}
Imports System
Imports System.Threading
Imports System.Reflection
Imports System.Reflection.Emit
Imports System.Security.Permissions

Public Class FieldBuilder_Sample
   Private Shared Function CreateType(currentDomain As AppDomain) As Type

      ' Create an assembly.
      Dim myAssemblyName As New AssemblyName()
      myAssemblyName.Name = "DynamicAssembly"
      Dim myAssembly As AssemblyBuilder = currentDomain.DefineDynamicAssembly(myAssemblyName, _
                                                AssemblyBuilderAccess.Run)
      ' Create a dynamic module in Dynamic Assembly.
      Dim myModuleBuilder As ModuleBuilder = myAssembly.DefineDynamicModule("MyModule")
      ' Define a public class named "MyClass" in the assembly.
      Dim myTypeBuilder As TypeBuilder = myModuleBuilder.DefineType("MyClass", _
                                          TypeAttributes.Public)
      ' Define a private String field named "MyField" in the type.
      Dim myFieldBuilder As FieldBuilder = myTypeBuilder.DefineField("MyField", _
                  GetType(String), FieldAttributes.Private Or FieldAttributes.Static)
      ' Create the constructor.
      Dim constructorArgs As Type() = {GetType(String)}
      Dim constructor As ConstructorBuilder = _
                  myTypeBuilder.DefineConstructor(MethodAttributes.Public, _
                           CallingConventions.Standard, constructorArgs)
      Dim constructorIL As ILGenerator = constructor.GetILGenerator()
      constructorIL.Emit(OpCodes.Ldarg_0)
      Dim superConstructor As ConstructorInfo = GetType(Object).GetConstructor(New Type() {})
      constructorIL.Emit(OpCodes.Call, superConstructor)
      constructorIL.Emit(OpCodes.Ldarg_0)
      constructorIL.Emit(OpCodes.Ldarg_1)
      constructorIL.Emit(OpCodes.Stfld, myFieldBuilder)
      constructorIL.Emit(OpCodes.Ret)

      ' Create the MyMethod method.
      Dim myMethodBuilder As MethodBuilder = myTypeBuilder.DefineMethod("MyMethod",  _
                        MethodAttributes.Public, GetType(String), Nothing)
      Dim methodIL As ILGenerator = myMethodBuilder.GetILGenerator()
      methodIL.Emit(OpCodes.Ldarg_0)
      methodIL.Emit(OpCodes.Ldfld, myFieldBuilder)
      methodIL.Emit(OpCodes.Ret)
      Console.WriteLine("Name               :" + myFieldBuilder.Name)
      Console.WriteLine("DeclaringType      :" + myFieldBuilder.DeclaringType.ToString())
      Console.WriteLine("Type               :" + myFieldBuilder.FieldType.ToString())
      Console.WriteLine("Token              :" + myFieldBuilder.GetToken().Token.ToString())
      Return myTypeBuilder.CreateType()
   End Function 'CreateType

   <PermissionSetAttribute(SecurityAction.Demand, Name:="FullTrust")> _
   Public Shared Sub Main()
      Try
         Dim myType As Type = CreateType(Thread.GetDomain())
         ' Create an instance of the "HelloWorld" class.
         Dim helloWorld As Object = Activator.CreateInstance(myType, New Object() {"HelloWorld"})
         ' Invoke the "MyMethod" method of the "MyClass" class.
         Dim myObject As Object = myType.InvokeMember("MyMethod", _
                     BindingFlags.InvokeMethod, Nothing, helloWorld, Nothing)
         Console.WriteLine("MyClass.MyMethod returned: " & Microsoft.VisualBasic.Chr(34) & myObject  & Microsoft.VisualBasic.Chr(34) )
     Catch e as Exception
            Console.WriteLine("Exception Caught "+e.Message)
     End Try
   End Sub 'Main
End Class 'FieldBuilder_Sample

Remarks

Get an instance of FieldBuilder by calling DefineField, DefineInitializedData, or DefineUninitializedData.

Note

The SetValue method is currently not supported. As a workaround, retrieve the FieldInfo by reflecting on the finished type and call SetValue to set the value of the field.

Properties

Attributes

Indicates the attributes of this field. This property is read-only.

DeclaringType

Indicates a reference to the Type object for the type that declares this field. This property is read-only.

FieldHandle

Indicates the internal metadata handle for this field. This property is read-only.

FieldType

Indicates the Type object that represents the type of this field. This property is read-only.

Module

Gets the module in which the type that contains this field is being defined.

Name

Indicates the name of this field. This property is read-only.

ReflectedType

Indicates the reference to the Type object from which this object was obtained. This property is read-only.

Methods

GetCustomAttributes(Boolean)

Returns all the custom attributes defined for this field.

GetCustomAttributes(Type, Boolean)

Returns all the custom attributes defined for this field identified by the given type.

GetToken()

Returns the token representing this field.

GetValue(Object)

Retrieves the value of the field supported by the given object.

IsDefined(Type, Boolean)

Indicates whether an attribute having the specified type is defined on a field.

SetConstant(Object)

Sets the default value of this field.

SetCustomAttribute(CustomAttributeBuilder)

Sets a custom attribute using a custom attribute builder.

SetCustomAttribute(ConstructorInfo, Byte[])

Sets a custom attribute using a specified custom attribute blob.

SetMarshal(UnmanagedMarshal)

Describes the native marshaling of the field.

SetOffset(Int32)

Specifies the field layout.

SetValue(Object, Object, BindingFlags, Binder, CultureInfo)

Sets the value of the field supported by the given object.

Explicit Interface Implementations

_FieldBuilder.GetIDsOfNames(Guid, IntPtr, UInt32, UInt32, IntPtr)

Maps a set of names to a corresponding set of dispatch identifiers.

_FieldBuilder.GetTypeInfo(UInt32, UInt32, IntPtr)

Retrieves the type information for an object, which can then be used to get the type information for an interface.

_FieldBuilder.GetTypeInfoCount(UInt32)

Retrieves the number of type information interfaces that an object provides (either 0 or 1).

_FieldBuilder.Invoke(UInt32, Guid, UInt32, Int16, IntPtr, IntPtr, IntPtr, IntPtr)

Provides access to properties and methods exposed by an object.

Extension Methods

GetCustomAttribute(MemberInfo, Type)
GetCustomAttribute(MemberInfo, Type, Boolean)
GetCustomAttribute<T>(MemberInfo)
GetCustomAttribute<T>(MemberInfo, Boolean)
GetCustomAttributes(MemberInfo)
GetCustomAttributes(MemberInfo, Boolean)
GetCustomAttributes(MemberInfo, Type)
GetCustomAttributes(MemberInfo, Type, Boolean)
GetCustomAttributes<T>(MemberInfo)
GetCustomAttributes<T>(MemberInfo, Boolean)
IsDefined(MemberInfo, Type)
IsDefined(MemberInfo, Type, Boolean)
GetMetadataToken(MemberInfo)
HasMetadataToken(MemberInfo)