Imports System
Imports System.Reflection
Imports System.Reflection.Emit
Class DemoMethodBuilder
Public Shared Sub AddMethodDynamically(ByVal myTypeBld As TypeBuilder, _
ByVal mthdName As String, _
ByVal mthdParams() As Type, _
ByVal returnType As Type, _
ByVal mthdAction As String)
Dim myMthdBld As MethodBuilder = myTypeBld.DefineMethod(mthdName, _
MethodAttributes.Public Or MethodAttributes.Static, _
returnType, _
mthdParams)
Dim ILout As ILGenerator = myMthdBld.GetILGenerator()
Dim numParams As Integer = mthdParams.Length
Dim x As Byte
For x = 0 To numParams - 1
ILout.Emit(OpCodes.Ldarg_S, x)
Next x
If numParams > 1 Then
Dim y As Integer
For y = 0 To (numParams - 1) - 1
Select Case mthdAction
Case "A"
ILout.Emit(OpCodes.Add)
Case "M"
ILout.Emit(OpCodes.Mul)
Case Else
ILout.Emit(OpCodes.Add)
End Select
Next y
End If
ILout.Emit(OpCodes.Ret)
End Sub
Public Shared Sub Main()
Dim myDomain As AppDomain = AppDomain.CurrentDomain
Dim asmName As New AssemblyName()
asmName.Name = "MyDynamicAsm"
Dim myAsmBuilder As AssemblyBuilder = myDomain.DefineDynamicAssembly(asmName, _
AssemblyBuilderAccess.RunAndSave)
Dim myModule As ModuleBuilder = myAsmBuilder.DefineDynamicModule("MyDynamicAsm", _
"MyDynamicAsm.dll")
Dim myTypeBld As TypeBuilder = myModule.DefineType("MyDynamicType", TypeAttributes.Public)
' Get info from the user to build the method dynamically.
Console.WriteLine("Let's build a simple method dynamically!")
Console.WriteLine("Please enter a few numbers, separated by spaces.")
Dim inputNums As String = Console.ReadLine()
Console.Write("Do you want to [A]dd (default) or [M]ultiply these numbers? ")
Dim myMthdAction As String = Console.ReadLine().ToUpper()
Console.Write("Lastly, what do you want to name your new dynamic method? ")
Dim myMthdName As String = Console.ReadLine()
' Process inputNums into an array and create a corresponding Type array
Dim index As Integer = 0
Dim inputNumsList As String() = inputNums.Split()
Dim myMthdParams(inputNumsList.Length - 1) As Type
Dim inputValsList(inputNumsList.Length - 1) As Object
Dim inputNum As String
For Each inputNum In inputNumsList
inputValsList(index) = CType(Convert.ToInt32(inputNum), Object)
myMthdParams(index) = GetType(Integer)
index += 1
Next inputNum
' Now, call the method building method with the parameters, passing the
' TypeBuilder by reference.
AddMethodDynamically(myTypeBld, myMthdName, myMthdParams, GetType(Integer), myMthdAction)
Dim myType As Type = myTypeBld.CreateType()
Dim description as String
If myMthdAction = "M" Then
description = "multiplying"
Else
description = "adding"
End If
Console.WriteLine("---")
Console.WriteLine("The result of {0} the values is: {1}", _
description, _
myType.InvokeMember(myMthdName, _
BindingFlags.InvokeMethod _
Or BindingFlags.Public _
Or BindingFlags.Static, _
Nothing, _
Nothing, _
inputValsList))
Console.WriteLine("---")
' If you are interested in seeing the MSIL generated dynamically for the method
' your program generated, change to the directory where you ran the compiled
' code sample and type "ildasm MyDynamicAsm.dll" at the prompt. When the list
' of manifest contents appears, click on "MyDynamicType" and then on the name of
' of the method you provided during execution.
myAsmBuilder.Save("MyDynamicAsm.dll")
Dim myMthdInfo As MethodInfo = myType.GetMethod(myMthdName)
Console.WriteLine("Your Dynamic Method: {0};", myMthdInfo.ToString())
End Sub
End Class