vb.net中，不使用FSO方法，怎么快速的得到文件夹的大小？

窗体上添加一个按钮，代码如下：
Public Class Form1

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Button1.Text = "稍等！"
Button1.Enabled = False

Dim MyFolder As String = "C:\Windows"
Dim MyDir As New System.IO.DirectoryInfo(MyFolder)
Dim MyInfo As String = MyFolder + "文件夹的大小是：" + CalculateDirectorySize(MyDir, True).ToString() + "字节。"
MessageBox.Show(MyInfo, "信息提示", _
MessageBoxButtons.OK, MessageBoxIcon.Information)

Button1.Text = "开始"
Button1.Enabled = True
End Sub

Public Shared Function CalculateDirectorySize(ByVal MyDirectory As System.IO.DirectoryInfo, ByVal IsSubDirectories As Boolean) As Long
Dim MySize As Long = 0
'检查包含的所有文件
Dim MyFiles() As System.IO.FileInfo = MyDirectory.GetFiles()
For Each MyFile As System.IO.FileInfo In MyFiles
MySize += MyFile.Length
Next
'检查包含的所有子文件夹
If (IsSubDirectories) Then
Dim MyDirs() As System.IO.DirectoryInfo = MyDirectory.GetDirectories()
For Each MyDir As System.IO.DirectoryInfo In MyDirs
MySize += CalculateDirectorySize(MyDir, True)
Next
End If
Return MySize
End Function

End Class

类库里File和Dir都没有直接获取文件夹大小的方法。如果不用FSO的话，要编程实现；
代码如下

Import system.io

Function GetFolderSize(ByVal DirPath As String, _

   Optional IncludeSubFolders as Boolean = True) As Long

  Dim lngDirSize As Long

  Dim objFileInfo As FileInfo

  Dim objDir As DirectoryInfo = New DirectoryInfo(DirPath)

  Dim objSubFolder As DirectoryInfo

Try

'add length of each file

  For Each objFileInfo In objDir.GetFiles()

    lngDirSize += objFileInfo.Length

  Next

  'call recursively to get sub folders

  'if you don't want this set optional

  'parameter to false

If IncludeSubFolders then

  For Each objSubFolder In objDir.GetDirectories()

    lngDirSize += GetFolderSize(objSubFolder.FullName)

  Next

End if

Catch Ex As Exception

Ex.tostring

End Try

   Return lngDirSize

End Function