vb.net 动态调用api

Imports System
Imports System.Runtime.InteropServices

Public Class DllInvoke
    Public Sub New(ByVal DLLPath As String)
        Me.hLib = DllInvoke.LoadLibrary(DLLPath)
    End Sub

    Protected Overrides Sub Finalize()
        Try
            DllInvoke.FreeLibrary(Me.hLib)
        Finally
            MyBase.Finalize()
        End Try
    End Sub

    <DllImport("kernel32.dll")> _
    Private Shared Function FreeLibrary(ByVal [lib] As IntPtr) As Boolean
    End Function

    <DllImport("kernel32.dll")> _
    Private Shared Function GetProcAddress(ByVal [lib] As IntPtr, ByVal funcName As String) As IntPtr
    End Function

    Public Function Invoke(ByVal APIName As String, ByVal t As Type) As [Delegate]
        Return Marshal.GetDelegateForFunctionPointer(DllInvoke.GetProcAddress(Me.hLib, APIName), t)
    End Function

    <DllImport("kernel32.dll")> _
    Private Shared Function LoadLibrary(ByVal path As String) As IntPtr
    End Function

    Private hLib As IntPtr
End Class

Imports System
Imports System.Runtime.CompilerServices
Imports System.Runtime.InteropServices
Imports System.Text

Public Class test

    Private Declare Function MessageBoxA Lib "user32" Alias "MessageBoxA" (ByVal hwnd As Integer, ByVal lpText As StringBuilder, ByVal lpCaption As StringBuilder, ByVal wType As Integer) As Long
    Private Delegate Function MessageBoxADelegate(ByVal hwnd As Integer, ByVal lpText As StringBuilder, ByVal lpCaption As StringBuilder, ByVal wType As Integer) As Long

    Public Shared Sub Main()
        Dim invoke As New DllInvoke("user32.dll")
        Dim mode As MessageBoxADelegate = DirectCast(invoke.Invoke("MessageBoxA", GetType(MessageBoxADelegate)), MessageBoxADelegate)
        mode.Invoke(0, New StringBuilder("haha"), New StringBuilder("title"), 0)
        Console.WriteLine("ok")
        Console.ReadLine()
    End Sub
End Class