Imports System.Reflection

Public Class FolderSelectDialog

    Public Class DialogResult
        Public ReturnCode As Integer
        Public FileName As String
    End Class

    Public Shared Function Show(ownerHandle As IntPtr, initialDirectory As String, title As String) As DialogResult
        Dim c_flags As BindingFlags = BindingFlags.Instance Or BindingFlags.[Public] Or BindingFlags.NonPublic
        Dim s_windowsFormsAssembly As Assembly = GetType(FileDialog).Assembly
        Dim s_iFileDialogType As Type = s_windowsFormsAssembly.[GetType]("System.Windows.Forms.FileDialogNative+IFileDialog")
        Dim s_createVistaDialogMethodInfo As MethodInfo = GetType(OpenFileDialog).GetMethod("CreateVistaDialog", c_flags)
        Dim s_onBeforeVistaDialogMethodInfo As MethodInfo = GetType(OpenFileDialog).GetMethod("OnBeforeVistaDialog", c_flags)
        Dim s_getOptionsMethodInfo As MethodInfo = GetType(FileDialog).GetMethod("GetOptions", c_flags)
        Dim s_setOptionsMethodInfo As MethodInfo = s_iFileDialogType.GetMethod("SetOptions", c_flags)
        Dim s_fosPickFoldersBitFlag As UInteger = CUInt(s_windowsFormsAssembly.[GetType]("System.Windows.Forms.FileDialogNative+FOS").GetField("FOS_PICKFOLDERS").GetValue(Nothing))
        Dim s_vistaDialogEventsConstructorInfo As ConstructorInfo = s_windowsFormsAssembly.[GetType]("System.Windows.Forms.FileDialog+VistaDialogEvents").GetConstructor(c_flags, Nothing, New Type() {GetType(FileDialog)}, Nothing)
        Dim s_adviseMethodInfo As MethodInfo = s_iFileDialogType.GetMethod("Advise")
        Dim s_unAdviseMethodInfo As MethodInfo = s_iFileDialogType.GetMethod("Unadvise")
        Dim s_showMethodInfo As MethodInfo = s_iFileDialogType.GetMethod("Show")

        Dim openFileDialog = New OpenFileDialog() With {
                    .AddExtension = False,
                    .CheckFileExists = False,
                    .DereferenceLinks = True,
                    .Filter = "Folders|",
                    .InitialDirectory = initialDirectory,
                    .Multiselect = False,
                    .Title = title
                }

        Dim iFileDialog = s_createVistaDialogMethodInfo.Invoke(openFileDialog, New Object() {})
        s_onBeforeVistaDialogMethodInfo.Invoke(openFileDialog, New Object() {iFileDialog})
        s_setOptionsMethodInfo.Invoke(iFileDialog, New Object() {CUInt(s_getOptionsMethodInfo.Invoke(openFileDialog, New Object() {})) Or s_fosPickFoldersBitFlag})

        Dim adviseParametersWithOutputConnectionToken = New Object() {s_vistaDialogEventsConstructorInfo.Invoke(New Object() {openFileDialog}), 0UI}
        s_adviseMethodInfo.Invoke(iFileDialog, adviseParametersWithOutputConnectionToken)

        Try
            Dim retVal As Integer = CInt(s_showMethodInfo.Invoke(iFileDialog, New Object() {ownerHandle}))

            Return New DialogResult() With {.ReturnCode = retVal, .FileName = openFileDialog.FileName}
        Finally
            s_unAdviseMethodInfo.Invoke(iFileDialog, New Object() {adviseParametersWithOutputConnectionToken(1)})
        End Try
    End Function

End Class