Visual Basic

Dim LPWSTR As UnmanagedType
Dim MyUnicodePointer As New MarshalAsAttribute(LPWSTR)

Dim MyStringPtr As Long = Marshal.StringToHGlobalAuto(MyString)

<VBFixedString(MAX_PATH), MarshalAs(UnmanagedType.ByValTStr, SizeConst:=MAX_PATH)> Public cFileName As String

Imports System.Runtime.InteropServices

Public Class Form1
   Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
      TreeView1.Nodes.Add(DriveToTreeNode("c"c))
   End Sub

   Private Sub TreeView1_AfterCollapse(ByVal sender As Object, ByVal e As System.Windows.Forms.TreeViewEventArgs) Handles TreeView1.AfterCollapse
      e.Node.Nodes.Clear()
      e.Node.Nodes.Add(New TreeNode With {.Tag = New NodeData With {.IsDirectory = True}}) ' add dummy node
   End Sub

   Private Sub TreeView1_BeforeExpand(ByVal sender As Object, ByVal e As System.Windows.Forms.TreeViewCancelEventArgs) Handles TreeView1.BeforeExpand
      ' only directories can have nodes
      e.Node.Nodes.Clear()
      EnumerateDirectory(e.Node)
   End Sub

   Private Sub TreeView1_MouseDoubleClick(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles TreeView1.MouseDoubleClick
      If e.Button = Windows.Forms.MouseButtons.Left Then
         Dim hti As TreeViewHitTestInfo = TreeView1.HitTest(TreeView1.PointToClient(MousePosition))
         If CType(hti.Node.Tag, NodeData).IsFile Then
            Dim fullpath As String = CType(hti.Node.Parent.Tag, NodeData).DirectoryPath & hti.Node.Text
            MessageBox.Show("Long Path: " & fullpath & vbCrLf & "Path Length: " & fullpath.Length.ToString() & _
                            vbCrLf & "Short Name: " & GetShortPathName(fullpath), _
                            hti.Node.Text, MessageBoxButtons.OK)
         End If
      End If
   End Sub

#Region "Drive Enumeration"
   Private Function DriveToTreeNode(ByVal drive As Char) As TreeNode
      Dim node As New TreeNode
      node.Text = drive.ToString().ToUpper()
      node.Tag = New NodeData With {.IsDirectory = True, .DirectoryPath = node.Text & ":\"}
      ' recursing all filedirectories would take too long for a drive
      ' so will handle it on each directory node expansion
      EnumerateDirectory(node, recursedirectories:=False)
      Return node
   End Function

   ' see: Naming Files, Paths, and Namespaces
   ' Maximum Path Length Limitation
   ' http://msdn.microsoft.com/en-us/library/windows/desktop/aa365247%28v=vs.85%29.aspx#maxpath
   Private Const LongPathPrefix As String = "\\?\"

   Private Sub EnumerateDirectory(ByVal node As TreeNode, Optional ByVal recursedirectories As Boolean = False)
      Dim path As String = CType(node.Tag, NodeData).DirectoryPath
      Dim findData As New WIN32_FIND_DATA

      Dim hFile As Microsoft.Win32.SafeHandles.SafeFileHandle
      hFile = FindFirstFile(LongPathPrefix & path & "*", findData)

      If hFile.DangerousGetHandle.ToInt32 = -1 Then
         ' just ignoring errors for this demo, most common is 5 - Access Denied
         ' System Error Codes
         ' http://msdn.microsoft.com/en-us/library/windows/desktop/ms681381%28v=vs.85%29.aspx
         'Dim [error] As Int32 = Marshal.GetLastWin32Error()
         'Stop
         Return
      Else
         Do
            If IsFlagSet(findData.dwFileAttributes, IO.FileAttributes.Directory) Then
               If findData.cFileName = "." Then Continue Do
               If findData.cFileName = ".." Then Continue Do
               Dim subdir As New TreeNode With {.Text = findData.cFileName, _
                                                .Tag = New NodeData With {.IsDirectory = True, _
                                                                           .DirectoryPath = path & findData.cFileName & "\" _
                                                                         } _
                                               }
               If recursedirectories Then
                  EnumerateDirectory(subdir, recursedirectories)
               Else
                  ' need to add a dummy node to make it expandable
                  subdir.Nodes.Add(New TreeNode With {.Tag = New NodeData With {.IsDirectory = True}})
               End If
               node.Nodes.Add(subdir)
            Else ' Filename
               node.Nodes.Add(New TreeNode With {.Text = findData.cFileName, .Tag = New NodeData With {.IsDirectory = False}})
            End If

         Loop While FindNextFile(hFile, findData)

         FindClose(hFile) ' make sure to close the handle
      End If

   End Sub

   Private Function IsFlagSet(ByVal value As System.ValueType, ByVal testflag As System.ValueType) As Boolean
      Dim val As UInt32 = CType(value, UInt32)
      Dim flag As UInt32 = CType(testflag, UInt32)
      Return (val And flag) = flag
   End Function

   <DllImport("kernel32.dll", CharSet:=CharSet.Unicode, SetLastError:=True, EntryPoint:="FindFirstFile")> _
   Private Shared Function FindFirstFile(<System.Runtime.InteropServices.In(), MarshalAs(UnmanagedType.LPWStr)> ByVal fileName As String, _
                                         <[In](), Out(), MarshalAs(UnmanagedType.LPStruct)> ByVal data As WIN32_FIND_DATA) As Microsoft.Win32.SafeHandles.SafeFileHandle
   End Function

   <DllImport("kernel32.dll", CharSet:=CharSet.Unicode, SetLastError:=True, EntryPoint:="FindNextFileW")> _
   Private Shared Function FindNextFile(ByVal hFindFile As Microsoft.Win32.SafeHandles.SafeFileHandle, _
                                        <[In](), Out(), MarshalAs(UnmanagedType.LPStruct)> ByVal ByvallpFindFileData As WIN32_FIND_DATA) As Boolean
   End Function

   <DllImport("kernel32.dll")> _
   Private Shared Function FindClose(ByVal hFindFile As Microsoft.Win32.SafeHandles.SafeFileHandle) As Boolean
   End Function

   <DllImport("kernel32.dll", SetLastError:=True, CharSet:=CharSet.Auto)> _
   Private Shared Function GetShortPathName(ByVal longPath As String, _
                                            <MarshalAs(UnmanagedType.LPTStr)> ByVal ShortPath As System.Text.StringBuilder, _
                                            <MarshalAs(Runtime.InteropServices.UnmanagedType.U4)> ByVal bufferSize As Integer) As Integer
   End Function

Quote:

In the ANSI version of this function, the name is limited to MAX_PATH characters. To extend this limit to 32,767 wide characters, call the Unicode version of the function and prepend "\\?\" to the path. For more information, see Naming a File.

Quote:

Damn. I swear to gawd I saw it say you needed to use the Ex version to make it happen.

If hFile.DangerousGetHandle.ToInt32 = -1 Then
   ' just ignoring errors for this demo, most common is 5 - Access Denied
   ' System Error Codes
   ' http://msdn.microsoft.com/en-us/library/windows/desktop/ms681381%28v=vs.85%29.aspx
   Dim [error] As Int32 = Marshal.GetLastWin32Error()
   Stop
   Return
Else

Private Structure WIN32_FIND_DATA
  Dim dwFileAttributes As UInt32
  Dim ftCreationTime As FILETIME
  Dim ftLastAccessTime As FILETIME
  Dim ftLastWriteTime As FILETIME
  Dim nFileSizeHigh As UInt32
  Dim nFileSizeLow As UInt32
  Dim dwReserved0 As UInt32
  Dim dwReserved1 As UInt32

  <VBFixedString(MAX_PATH), MarshalAs(UnmanagedType.ByValTStr, SizeConst:=MAX_PATH)> Public cFileName As String
  <VBFixedString(14), MarshalAs(UnmanagedType.ByValTStr, SizeConst:=14)> Public cAlternate As String

End Structure

<StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Unicode), BestFitMapping(False)> _
Private Class WIN32_FIND_DATA
   <MarshalAs(UnmanagedType.U4)> Public dwFileAttributes As IO.FileAttributes = 8208
   <MarshalAs(UnmanagedType.U4)> Private ftCreationTime_dwLowDateTime As UInt32 = 0
   <MarshalAs(UnmanagedType.U4)> Private ftCreationTime_dwHighDateTime As UInt32 = 0
   <MarshalAs(UnmanagedType.U4)> Private ftLastAccessTime_dwLowDateTime As UInt32 = 0
   <MarshalAs(UnmanagedType.U4)> Private ftLastAccessTime_dwHighDateTime As UInt32 = 0
   <MarshalAs(UnmanagedType.U4)> Private ftLastWriteTime_dwLowDateTime As UInt32 = 0
   <MarshalAs(UnmanagedType.U4)> Private ftLastWriteTime_dwHighDateTime As UInt32 = 0
   <MarshalAs(UnmanagedType.U4)> Public nFileSizeHigh As UInt32 = 0
   <MarshalAs(UnmanagedType.U4)> Public nFileSizeLow As UInt32 = 0
   <MarshalAs(UnmanagedType.U4)> Public dwReserved0 As UInt32 = 0
   <MarshalAs(UnmanagedType.U4)> Public dwReserved1 As UInt32 = 0

   ' Note: by changing the cFileName size constant from 260 to 32767 to handle long
   ' path names, it appears that cAlternateFileName always returns blank
   ' if the ShortPathName is needed, then use the GetShortPathName function
   ' http://msdn.microsoft.com/en-us/library/windows/desktop/aa364989%28v=vs.85%29.aspx
   <MarshalAs(UnmanagedType.ByValTStr, SizeConst:=32767)> Public cFileName As String = " "
   <MarshalAs(UnmanagedType.ByValTStr, SizeConst:=14)> Public cAlternateFileName As String = " "

Quote:

... let alone trying to remember the path of the namespace.

Imports sri = System.Runtime.InteropServices
Imports lok = System.Runtime.InteropServices.LayoutKind
Imports umt = System.Runtime.InteropServices.UnmanagedType

<sri.StructLayout(lok.Sequential)> _
Public Class Class1
   <sri.MarshalAs(umt.U4)> Public Fred As UInt32
End Class