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Updated: VB code now uses IntPtr instead of StringBuilder - see sample below
Using StringBuilder for the buffer does not work since this function returns the names as a bunch of strings separated by the null character ('\0'). So StringBuilder would only report the first item. Therefore we store it in a char array, which can later be converted to a bunch of strings.
Tips & Tricks:
Please add some!
Sample Code:
UInt32 dwRequired = 0;
char[] buffer = new char[260];
if (!GetVolumePathNamesForVolumeName(volumeName, buffer, (uint)buffer.Length, ref dwRequired))
{
// Not enough room in buffer perhaps? Try a bigger one
buffer = new char[dwRequired];
if (!GetVolumePathNamesForVolumeName(volumeName, buffer, (uint)buffer.Length, ref dwRequired))
throw new Win32Exception();
}
Sample Code 2:
public List<string> GetMountPointsForVolume(string volumeDeviceName)
{
List<string> result = new List<string>();
// GetVolumePathNamesForVolumeName is only available on Windows XP/2003 and above
int osVersionMajor = Environment.OSVersion.Version.Major;
int osVersionMinor = Environment.OSVersion.Version.Minor;
if (osVersionMajor < 5 || (osVersionMajor == 5 && osVersionMinor < 1))
{
return result;
}
if (!GetVolumePathNamesForVolumeNameW(volumeDeviceName, buffer, lpcchReturnLength, ref lpcchReturnLength))
{
throw new Win32Exception(Marshal.GetLastWin32Error());
}
string[] mounts = buffer.Split('\0');
foreach (string mount in mounts)
{
if (mount.Length > 0)
{
result.Add(mount);
}
}
}
catch (Exception ex)
{
Console.WriteLine(ex.ToString());
}
return result;
}
Sample VB.Net Code (.Net Framework 3.5sp1)
Imports System.Runtime.InteropServices
Module Module1
Partial Public Class PInvoke
' Have to use Pointer to return pathnames, StringBuilder only returns first NULL-terminated stgring
<DllImportAttribute("kernel32.dll", _
CharSet:=CharSet.Unicode, _
EntryPoint:="GetVolumePathNamesForVolumeNameW", _
SetLastError:=True)>
Public Shared Function GetMountPointsPtr(ByVal sVolumeName As String, _
ByVal lpBuffer As IntPtr, _
ByVal uintBufferLen As UInteger, _
ByRef uintReturnLen As UInteger) _
As <MarshalAs(UnmanagedType.Bool)> Boolean
End Function
End Class
Sub Main()
ListMountPoints()
End Sub
' if no Volume GUID passed to sub, use the one corresponding to my USB stick
Private Sub ListMountPoints(Optional strVolumeName As String = "\\?\Volume{9a615499-414c-11e0-bd72-78e7d1722cbc}\")
Try
Dim uintBufferLen As UInteger = CUInt((IntPtr.Size) / 2)
Dim uintRequiredBufferLen As UInteger = 0
Dim Win32ErrVal As Integer = 0
Dim lpBuffer As IntPtr = Marshal.AllocHGlobal(IntPtr.Size)
' call function to get Required Buffer Length first
PInvoke.GetMountPointsPtr(strVolumeName, lpBuffer, uintBufferLen, uintRequiredBufferLen)
Win32ErrVal = Marshal.GetLastWin32Error()
If Win32ErrVal = 234 Then
'expected return value (ERROR_MORE_DATA), as our initial buffer is not large enough
ElseIf Win32ErrVal = 2 Then
' oops
Throw New ApplicationException("Invalid volume specified?")
Else
Throw New ApplicationException("Exception getting required buffer size.")
End If
' reallocate the IntPtr with the right size
lpBuffer = Marshal.ReAllocHGlobal(lpBuffer, CType(uintRequiredBufferLen * 2, IntPtr))
' now set the buffer length
uintBufferLen = uintRequiredBufferLen
'zero out the length indicator
uintRequiredBufferLen = 0
' reset errVal
Win32ErrVal = 0
If CBool(Not (PInvoke.GetMountPointsPtr(strVolumeName, lpBuffer, _
uintBufferLen, uintRequiredBufferLen))) Then
Throw New ApplicationException("Exception Occured @ line 54!")
End If
' retrieve the mountpoints(s)
Dim strOutput As String = Marshal.PtrToStringUni(lpBuffer, CInt(uintRequiredBufferLen))
If Not (CBool(lpBuffer = IntPtr.Zero)) Then
Marshal.FreeHGlobal(lpBuffer)
lpBuffer = IntPtr.Zero
End If
Console.WriteLine(strVolumeName + " has the following mountpoints: " _
+ vbCrLf + strOutput.ToString)
Catch ex As Exception
Dim errVal As Integer = Marshal.GetLastWin32Error()
Console.WriteLine(ex.Message + " The last Win32 error was: " + CStr(errVal))
End Try
End Sub
End Module
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10/2/2011 2:35:57 AM - txzhgh-89.110.151.174
An IntPtr is a pointer to a memory location (unmanaged) that adapts to the platform it is running on (64-bit, etc.) UNLIKE a standard int/Integer. You should always use this type for unmanaged calls that require it, even though an int will appear to work on your development machine.
1/13/2008 4:00:13 AM - Damon Carr-72.43.165.29
Click to read this page
10/2/2011 2:35:57 AM - txzhgh-89.110.151.174
Click to read this page
10/2/2011 2:35:57 AM - txzhgh-89.110.151.174
Click to read this page
10/2/2011 2:35:57 AM - txzhgh-89.110.151.174
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