' 导入命名空间
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 myConstructor As ConstructorBuilder = _
                     myTypeBuilder.DefineConstructor(MethodAttributes.Public, _
                              CallingConventions.Standard, constructorArgs)
      Dim constructorIL As ILGenerator = myConstructor.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)
      If myFieldBuilder.Attributes.Equals(FieldAttributes.Static) Then
         Console.WriteLine("Field attribute defined as Static")
      Else
         If myFieldBuilder.Attributes.Equals(FieldAttributes.Static Or FieldAttributes.Private) Then
            Console.WriteLine("Field attributes are Static and Private")
         End If
      End If
      Console.WriteLine("ReflectedType of Field is: " & myFieldBuilder.ReflectedType.ToString())
      Return myTypeBuilder.CreateType()

   End Function 'CreateType

   <PermissionSetAttribute(SecurityAction.Demand, Name:="FullTrust")> _
   Public Shared Sub Main()
      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"  of the "MyClass".
      Dim myObject As Object = myType.InvokeMember("MyMethod", _
               BindingFlags.InvokeMethod, Nothing, helloWorld, Nothing)
      Console.WriteLine("MyClass.MyMethod returned: """ & myObject & """")
   End Sub
End Class