DllLoader Class for VB.NET

Imports System
Imports System.Runtime.InteropServices

Public Class DllLoader(Of T)
    Implements IDisposable

    Private _dllHandle As IntPtr
    Private _disposed As Boolean = False

    Public Property [Function] As T

    Public Sub New(dllPath As String, functionName As String)
        _dllHandle = LoadLibrary(dllPath)
        If _dllHandle = IntPtr.Zero Then
            Throw New Exception("Failed to load DLL: " & dllPath)
        End If

        Dim functionPtr As IntPtr = GetProcAddress(_dllHandle, functionName)
        If functionPtr = IntPtr.Zero Then
            Throw New Exception("Failed to find function: " & functionName)
        End If

        [Function] = Marshal.GetDelegateForFunctionPointer(Of T)(functionPtr)
    End Sub

    Protected Overrides Sub Finalize()
        Dispose(False)
        MyBase.Finalize()
    End Sub

    Public Sub Dispose() Implements IDisposable.Dispose
        Dispose(True)
        GC.SuppressFinalize(Me)
    End Sub

    Protected Overridable Sub Dispose(disposing As Boolean)
        If Not _disposed Then
            If disposing Then
                ' マネージドリソースの解放
            End If

            ' アンマネージドリソースの解放
            If _dllHandle <> IntPtr.Zero Then
                FreeLibrary(_dllHandle)
                _dllHandle = IntPtr.Zero
            End If

            _disposed = True
        End If
    End Sub

    <DllImport("kernel32.dll", CharSet:=CharSet.Unicode, SetLastError:=True)>
    Private Shared Function LoadLibrary(lpFileName As String) As IntPtr
    End Function

    <DllImport("kernel32.dll", CharSet:=CharSet.Ansi, SetLastError:=True)>
    Private Shared Function GetProcAddress(hModule As IntPtr, lpProcName As String) As IntPtr
    End Function

    <DllImport("kernel32.dll", SetLastError:=True)>
    Private Shared Function FreeLibrary(hModule As IntPtr) As <MarshalAs(UnmanagedType.Bool)> Boolean
    End Function
End Class