CreateFile problem in Win7 with a shared printer

Question

I have a VB2005 process in WinXP that prints to a local usb printer by using ' createfile' and 'safefilehandles'. When I run this program in Win7, or if I try to use a usb printer on a Win7 machine the CreateFile process fails, by not getting a file handle. The printer is usually on the local machine and it is shared and the CreateFile function uses the syntax "\\server\PrinterShareName".  I have cannot find any method that sheds light on the problem. Any ideas? Thanks...

Answer 1

Hi RobFischer,

Could you please show some code that use the local printer? And did you use try{}catch{} or GetLastError to check if your code throws the errors in the Windows 7 system? Then did you check if your code needes the administrator privileges, since Windows Vista and 7 is a UAC system, please try to run your code as administrator, and then try to use the manifest to change the UAC setting for your application: http://msdn.microsoft.com/en-us/library/bb756929.aspx

Other resource I found, http://support.microsoft.com/kb/154078/EN-US this KB introduce one way to send data to printer visa Win32 API. And .Net just provides the class to handle the Printer, such as: PrintDialog Class

Sincerely,

---

Bob Bao [MSFT]
MSDN Community Support | Feedback to us

Answer 2

Here is the code for my test project, a Form1  and Module1 project.  This project is able to load a file successfully ("c:\xfer\testfile.txt") and is also able to get a handle for a printer attached to a WinXP machine ("\\PIO-WS3-FH\LaserPrinter").  It cannot get a handle for a usb printer attached to the local Win7 pc and shared as "\\RWF-HP\\ZebraHP".

The error is that the handle.Isvalid is false

I must send raw code directly to a printer without using the printer drivers, so the printer executes its internal command structure. This is a Zebra label printer and I want to send CPCL language commands.  So the printDialog class is not useful in this instance.

Thanks... I will try your suggestions concerning admin privileges and manifests.

-------------------------------------------------------------

Form1:

     

Imports Microsoft.Win32.SafeHandles
'
Public Class Form1

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        Dim s As SafeFileHandle
        ' s = New UnmanagedFileLoader("c:\xfer\testfile.txt").Handle
        s = New UnmanagedFileLoader("\\RWF-HP\\ZebraHP").Handle
        s = New UnmanagedFileLoader("\\RWF-HP\ZDesigner RW 420").Handle   '\\\\.\\PhysicalDrive0"
        s = New UnmanagedFileLoader("\\RWF-COMPAQ\HP Color Laserjet 1600").Handle
        s = New UnmanagedFileLoader("\\PIO-WS3-FH\LaserPrinter").Handle   'OK!!!!!! it is WINXP !!!!!
    End Sub

End Class

----------------------------------------------------------------------------

Module1:

Imports System
Imports Microsoft.Win32.SafeHandles
Imports System.Runtime.InteropServices
Imports System.ComponentModel

Module SafeHandlesExample

    Sub Main()
        Try

            Dim loader As New UnmanagedFileLoader("c:\xfer\testfile.txt")

        Catch e As Exception
            Console.WriteLine(e)
        End Try
        Console.ReadLine()

    End Sub
End Module


Class UnmanagedFileLoader

    Public Const FILE_ATTRIBUTE_NORMAL As Short = &H80
    Public Const INVALID_HANDLE_VALUE As Short = -1
    Public Const GENERIC_READ As Long = &H80000000
    Public Const GENERIC_WRITE As UInteger = &H40000000
    Public Const CREATE_NEW As UInteger = 1
    Public Const CREATE_ALWAYS As UInteger = 2
    Public Const OPEN_EXISTING As UInteger = 3
    Public Const RW As UInteger = &H1D000000


    ' Use interop to call the CreateFile function.
    ' For more information about CreateFile,
    ' see the unmanaged MSDN reference library.
    <DllImport("kernel32.dll", SetLastError:=True)> _
    Private Shared Function CreateFile(ByVal lpFileName As String, ByVal dwDesiredAccess As System.UInt32, ByVal dwShareMode As System.UInt32, ByVal lpSecurityAttributes As IntPtr, ByVal dwCreationDisposition As System.UInt32, ByVal dwFlagsAndAttributes As System.UInt32, ByVal hTemplateFile As IntPtr) As SafeFileHandle


    End Function

    Private handleValue As SafeFileHandle = Nothing

    Public Sub New(ByVal Path As String)
        Load(Path)


    End Sub


    Public Sub Load(ByVal Path As String)
        If Path Is Nothing AndAlso Path.Length = 0 Then
            Throw New ArgumentNullException("Path")
        End If


        ' Try to open the file.
        ' handleValue = CreateFile(Path, GENERIC_WRITE, 0, IntPtr.Zero, OPEN_EXISTING, 0, IntPtr.Zero)
        handleValue = CreateFile(Path, RW, 0, Nothing, OPEN_EXISTING, 0, Nothing)  'doc says that last must be NULL, nothing in vb

        ' If the handle is invalid,
        ' get the last Win32 error 
        ' and throw a Win32Exception.
        If handleValue.IsInvalid Then
            Marshal.ThrowExceptionForHR(Marshal.GetLastWin32Error())
            MsgBox("No Good")
        End If

    End Sub

    Public ReadOnly Property Handle() As SafeFileHandle
        Get
            ' If the handle is valid,
            ' return it.
            If Not handleValue.IsInvalid Then
                Return handleValue
            Else
                Return Nothing
            End If
        End Get
    End Property
End Class


'End Module

Answer 3

 This is a VB 2005 project I am working with.  I am looking at the application manifest methods. Is this manifest process as complicated as it seems?

Answer 4

I have turned off UAC and the CreateFile problem remains. It appears to be related to a usb device attached to Win7, and adding a manifest to change UAC is unnecessary. Is there anything else to do? Thanks for your help thusfar.

Answer 5

Hmm, try to read this thread that has similar issue with you: http://social.msdn.microsoft.com/Forums/en-us/wdk/thread/d6f6d0a8-9c92-43e1-b9f9-82ec9cbc1a2f I know CreateFile can used to get the printer, I/O handle, but I still recommend you to use the .Net solution to control the printer, or via the wrapped Win32 API to connect the printer, such from http://support.microsoft.com/kb/154078/EN-US

---

Bob Bao [MSFT]
MSDN Community Support | Feedback to us

Answer 6

I have tried the methods in those other threads and each takes me to a dead end. The core issue is this: CreateFile and SafeFileHandles are unable to open a valid handle on a usb device attached on a Win7 machine with all security and UAC disabled, and the device is shared.  The same exact code works in WinXP, and on Win7 it works for a disk file and it works for a usb device attached to a remote WinXP machine.   This sounds quite fundamental and perhaps the CreateFile just will not work in this case. Is there a proper place to request Microsoft look into this as a bug report?    My other options for solving the problem (such as using a report generator and the windows printer drivers) are much less efficient .    I greatly appreciate your time helping me with this, Bob.

Answer 7

Try Connect site for Microsoft Product feedback. And if you have the detailed report for this issue, you could share it on the site.

---

Bob Bao [MSFT]
MSDN Community Support | Feedback to us

Answer 8

Thanks for your help Bob. I will pursue it on that site.

Answer 9

Hey Rob did you ever get any useful information on this problem? I am having the exact same problem. I tried clicking over to the Connect site and searching but I couldn't find it. 

Answer 10

Strange as it may seem, changing the dwCreationDisposition parameter of CreateFile from OPEN_EXISTING, which is suggested by the documentation, to OPEN_ALWAYS solved the problem for me.