C# Signature:

[DllImport("Kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
extern static bool GetVolumeInformation(
  string RootPathName,
  StringBuilder VolumeNameBuffer,
  int VolumeNameSize,
  out uint VolumeSerialNumber,
  out uint MaximumComponentLength,
  out uint FileSystemFlags,
  StringBuilder FileSystemNameBuffer,
  int nFileSystemNameSize);

VB Signature:

  Private Declare Auto Function GetVolumeInformation Lib "kernel32.dll" ( _
     ByVal RootPathName As String, _
     ByVal VolumeNameBuffer As System.Text.StringBuilder, _
     ByVal VolumeNameSize As UInt32, _
     ByRef VolumeSerialNumber As UInt32, _
     ByRef MaximumComponentLength As UInt32, _
     ByRef FileSystemFlags As UInt32, _
     ByVal FileSystemNameBuffer As System.Text.StringBuilder, _
     ByVal FileSystemNameSize As UInt32) As UInt32

User-Defined Types:

None.

Notes:

The VolumeSerialNumber is not optional with this signature!!!

Tips & Tricks:

If you specify RootPathName as a driveletter (eg not a volume name) then you have to terminate it with a backslash.

I had to change the return type to int and compare with 0. The bool return value didn't work for me.

Adding the attribute [return: MarshalAs(UnmanagedType.Bool)] should make the bool return value work.

Sample Code:

StringBuilder volname = new StringBuilder(261);
StringBuilder fsname = new StringBuilder(261);
uint sernum, maxlen, flags;
if(!GetVolumeInformation("c:\\", volname, volname.Capacity, out sernum, out maxlen, out flags, fsname, fsname.Capacity))
    Marshal.ThrowExceptionForHR(Marshal.GetHRForLastWin32Error());
string volnamestr = volname.ToString();
string fsnamestr = fsname.ToString();

Sample code - VB.NET:

   ''' <summary>
   ''' Returns volume name and serial number, maximum path component length, and filesystem name and flags
   ''' for the specified directory. Works with UNC. Can throw an exception.
   ''' </summary>
   ''' <param name="FolderPath">Path to drive or shared folder to find about.</param>
   ''' <param name="VolumeName">Returns volume name.</param>
   ''' <param name="VolumeSerialNumber">Returns volume serial number.</param>
   ''' <param name="MaxComponentLength">Returns max. path component lenght.</param>
   ''' <param name="FileSystemFlags">Returns file system flags - see http://msdn.microsoft.com/en-us/library/aa364993(VS.85).aspx</param>
   ''' <param name="FileSystemName">Returns file system name.</param>
   ''' <remarks></remarks>
   Public Sub GetVolumeInfo( _
     ByVal FolderPath As String, _
     ByRef VolumeName As String, _
     ByRef VolumeSerialNumber As String, _
     ByRef MaxComponentLength As UInt32, _
     ByRef FileSystemFlags As UInt32, _
     ByRef FileSystemName As String)
      ' see http://msdn.microsoft.com/en-us/library/aa364993(VS.85).aspx
      Dim sRootFolder As String = IO.Path.GetPathRoot(FolderPath)
      If Not sRootFolder.EndsWith("\") Then sRootFolder &= "\"
      Const MAX_PATH As Integer = &H104
      Dim volname As New System.Text.StringBuilder(MAX_PATH + 1)
      Dim fsname As New System.Text.StringBuilder(MAX_PATH + 1)
      Dim sernum As UInt32
      Dim RetVal As UInt32 = GetVolumeInformation(sRootFolder, volname, volname.Capacity, _
                          sernum, MaxComponentLength, FileSystemFlags, _
                          fsname, fsname.Capacity)
      If RetVal = 0 Then Throw New System.ComponentModel.Win32Exception(Err.LastDllError)
      VolumeName = volname.ToString
      FileSystemName = fsname.ToString

      Dim hpart, lpart As Integer
      hpart = sernum \ 65536
      lpart = sernum - hpart * 65536L
      VolumeSerialNumber = Hex(hpart).PadLeft(4, "0"c) & "-" & Hex(lpart).PadLeft(4, "0"c)
   End Sub

Alternative Managed API:

System.Management.ManagementObject("Win32_LogicalDisk.DeviceID=" & DriveLetter & ":")

Sample:

Private Function GetVolumeSerial(ByVal DriveLetter As String) As String

    'Check for valid drive letter argument.
    Dim ValidDriveLetters As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    If ValidDriveLetters.IndexOf(DriveLetter) <> -1 Then
    If DriveLetter.Length = 1 Then
        Dim Disk As New System.Management.ManagementObject("Win32_LogicalDisk.DeviceID=""" & DriveLetter & ":""")
        Dim DiskProperty As System.Management.PropertyData
        For Each DiskProperty In Disk.Properties
        If DiskProperty.Name = "VolumeSerialNumber" Then
            Return DiskProperty.Value.ToString  '.ToString 'Return the volume serial number.
        End If
        Next DiskProperty
    End If
    End If
    Return Nothing 'Invalid drive letter.

End Function

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