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(, New StringBuilder("haha"), New StringBuilder("title"), )

        Console.WriteLine("ok")

        Console.ReadLine()

    End Sub

End Class