Question

I have to use CreateFile imported from kernel32.dll in some VB .NET project to obtain some handle for WinUSB further functions.

The question is do I need to destroy somehow/something after CreateFile when I don’t need the handle anymore?

The second question is I use WinUsb_Initialize() with CreateFile returned handle to obtain another handle for WinUSB purposes. Do I need to make some cleaning too?

Thanks in advance,

---

   <DllImport("kernel32.dll",
            SetLastError:=True,
            CharSet:=CharSet.Auto)> _
    Private Shared Function CreateFile(ByVal lpFileName As String,
                                       ByVal dwDesiredAccess As Int32,
                                       ByVal dwShareMode As UInt32,
                                       ByVal lpSecurityAttributes As IntPtr,
                                       ByVal dwCreationDisposition As UInt32,
                                       ByVal dwFlagsAndAttributes As UInt32,
                                       ByVal hTemplateFile As IntPtr) As SafeFileHandle
    End Function

    <DllImport("kernel32.dll",
        CharSet:=CharSet.Auto,
        SetLasterror:=True)>
    Public Shared Function CloseHandle(ByVal Handle As Integer) As <MarshalAs(UnmanagedType.Bool)> Boolean
    End Function

Now I read somewhere if I use safehandlers in CreateFile there is no need to CloseHandle.
This is my “Disconnect” code

Dim ErrorStatus As Integer = 0

If hWinUSBInterface <> INVALID_HANDLE_VALUE Then
    WinUsb_Free(hWinUSBInterface)
    hWinUSBInterface = INVALID_HANDLE_VALUE
End If

If hDevice <> INVALID_HANDLE_VALUE Then

    'hDevice = INVALID_HANDLE_VALUE
    'RaiseEvent Error(ErrorStatus, "Disconnect")

    If CloseHandle(hDevice) Then
        hDevice = INVALID_HANDLE_VALUE
        RaiseEvent Disconnected()
    Else
        ErrorStatus = Err.LastDllError
        RaiseEvent Error(ErrorStatus, "Disconnect")
    End If

End If

Answer 1

The HANDLE you obtained from CreateFile() must be released by pinvoking CloseHandle().

The WINUSB_INTERFACE_HANDLE you obtained from WinUSB_Initialize() must be released by pinvoking WinUSB_Free().

Note that these requirements are spelled out in detail in the MSDN Library articles for these functions.