Imports System
Imports System.Threading
Imports System.Reflection
Imports System.Reflection.Emit
Class PropertyBuilderDemo
Public Shared Function BuildDynamicTypeWithProperties() As Type
Dim myDomain As AppDomain = Thread.GetDomain()
Dim myAsmName As New AssemblyName()
myAsmName.Name = "MyDynamicAssembly"
' To generate a persistable assembly, specify AssemblyBuilderAccess.RunAndSave.
Dim myAsmBuilder As AssemblyBuilder = myDomain.DefineDynamicAssembly(myAsmName, _
AssemblyBuilderAccess.RunAndSave)
' Generate a persistable, single-module assembly.
Dim myModBuilder As ModuleBuilder = _
myAsmBuilder.DefineDynamicModule(myAsmName.Name, myAsmName.Name & ".dll")
Dim myTypeBuilder As TypeBuilder = myModBuilder.DefineType("CustomerData", TypeAttributes.Public)
' Define a private field to hold the property value.
Dim customerNameBldr As FieldBuilder = myTypeBuilder.DefineField("customerName", _
GetType(String), FieldAttributes.Private)
' The last argument of DefineProperty is Nothing, because the
' property has no parameters. (If you don't specify Nothing, you must
' specify an array of Type objects. For a parameterless property,
' use an array with no elements: New Type() {})
Dim custNamePropBldr As PropertyBuilder = _
myTypeBuilder.DefineProperty("CustomerName", _
PropertyAttributes.HasDefault, _
GetType(String), _
Nothing)
' The property set and property get methods require a special
' set of attributes.
Dim getSetAttr As MethodAttributes = _
MethodAttributes.Public Or MethodAttributes.SpecialName _
Or MethodAttributes.HideBySig
' Define the "get" accessor method for CustomerName.
Dim custNameGetPropMthdBldr As MethodBuilder = _
myTypeBuilder.DefineMethod("GetCustomerName", _
getSetAttr, _
GetType(String), _
Type.EmptyTypes)
Dim custNameGetIL As ILGenerator = custNameGetPropMthdBldr.GetILGenerator()
custNameGetIL.Emit(OpCodes.Ldarg_0)
custNameGetIL.Emit(OpCodes.Ldfld, customerNameBldr)
custNameGetIL.Emit(OpCodes.Ret)
' Define the "set" accessor method for CustomerName.
Dim custNameSetPropMthdBldr As MethodBuilder = _
myTypeBuilder.DefineMethod("get_CustomerName", _
getSetAttr, _
Nothing, _
New Type() {GetType(String)})
Dim custNameSetIL As ILGenerator = custNameSetPropMthdBldr.GetILGenerator()
custNameSetIL.Emit(OpCodes.Ldarg_0)
custNameSetIL.Emit(OpCodes.Ldarg_1)
custNameSetIL.Emit(OpCodes.Stfld, customerNameBldr)
custNameSetIL.Emit(OpCodes.Ret)
' Last, we must map the two methods created above to our PropertyBuilder to
' their corresponding behaviors, "get" and "set" respectively.
custNamePropBldr.SetGetMethod(custNameGetPropMthdBldr)
custNamePropBldr.SetSetMethod(custNameSetPropMthdBldr)
Dim retval As Type = myTypeBuilder.CreateType()
' Save the assembly so it can be examined with Ildasm.exe,
' or referenced by a test program.
myAsmBuilder.Save(myAsmName.Name & ".dll")
return retval
End Function 'BuildDynamicTypeWithProperties
Public Shared Sub Main()
Dim custDataType As Type = BuildDynamicTypeWithProperties()
Dim custDataPropInfo As PropertyInfo() = custDataType.GetProperties()
Dim pInfo As PropertyInfo
For Each pInfo In custDataPropInfo
Console.WriteLine("Property '{0}' created!", pInfo.ToString())
Next pInfo
Console.WriteLine("---")
' Note that when invoking a property, you need to use the proper BindingFlags -
' BindingFlags.SetProperty when you invoke the "set" behavior, and
' BindingFlags.GetProperty when you invoke the "get" behavior. Also note that
' we invoke them based on the name we gave the property, as expected, and not
' the name of the methods we bound to the specific property behaviors.
Dim custData As Object = Activator.CreateInstance(custDataType)
custDataType.InvokeMember("CustomerName", BindingFlags.SetProperty, Nothing, _
custData, New Object() {"Joe User"})
Console.WriteLine("The customerName field of instance custData has been set to '{0}'.", _
custDataType.InvokeMember("CustomerName", BindingFlags.GetProperty, _
Nothing, custData, New Object() {}))
End Sub 'Main
End Class 'PropertyBuilderDemo
' --- O U T P U T ---
' The output should be as follows:
' -------------------
' Property 'System.String CustomerName [System.String]' created!
' ---
' The customerName field of instance custData has been set to 'Joe User'.
' -------------------