Invalid Parameter: Name handle Exception

Question

I am using VB.Net code to print barcode label in Zebra TLP 2844 printer. And the printer is connected to system by USB port. When i execute the code i get an error "Invalid Parameter : Name handle" in the line outFile = New FileStream(_SafeFileHandle, FileAccess.Write) . Can you please help me to rectify this.
As this is a USB port So i shared the printer and used the UNC path. But still i get the error. Below is the complete code

Name Spaces
Imports System.IO
Imports System.Runtime.InteropServices

 Here is the button click code

 Dim _print as new ZebraPrint
_print.StartWrite("//ComputerName/PrinterSharedName")
dim _Text as String = "Print test"
_print.Write("A30,120,0,4,2,1,N,""" & _Text & """")
_print.EndWrite()

 

Class

 Public Class ZebraPrint
#Region " Private constants "
Private Const GENERIC_WRITE As Integer = &H40000000
Private Const OPEN_EXISTING As Integer = 3
#End Region

  #Region " Private members "
Private _SafeFileHandle As Microsoft.Win32.SafeHandles.SafeFileHandle
Private _fileWriter As StreamWriter
Private _outFile As FileStream

#End Region

  #Region " private structures "
<StructLayout(LayoutKind.Sequential)> _
Public Structure SECURITY_ATTRIBUTES
Private nLength As Integer
Private lpSecurityDescriptor As Integer
Private bInheritHandle As Integer
End Structure

#End Region

  #Region " com calls "
Private Declare Function CreateFile Lib "kernel32" Alias "CreateFileA" (ByVal lpFileName As String, ByVal dwDesiredAccess As Integer, ByVal dwShareMode As Integer, <MarshalAs(UnmanagedType.Struct)> ByRef lpSecurityAttributes As SECURITY_ATTRIBUTES, ByVal dwCreationDisposition As Integer, ByVal dwFlagsAndAttributes As Integer, ByVal hTemplateFile As Integer) As Microsoft.Win32.SafeHandles.SafeFileHandle

#End Region
#Region " Public methods "
Public Sub StartWrite(ByVal printerPath As String)
Dim SA As SECURITY_ATTRIBUTES

  _SafeFileHandle = CreateFile(printerPath, GENERIC_WRITE, 0, SA, OPEN_EXISTING, 0, 0)

  Try

                _outFile = New FileStream(_SafeFileHandle, FileAccess.Write)

                _fileWriter = New StreamWriter(_outFile)

            Catch ex As Exception

                System.Windows.Forms.MessageBox.Show("Can not find printer.", "Warning", Windows.Forms.MessageBoxButtons.OK, Windows.Forms.MessageBoxIcon.Error, Windows.Forms.MessageBoxDefaultButton.Button1)

            End Try

 

        End Sub

 

        Public Sub Write(ByVal rawLine As String)

            If _fileWriter IsNot Nothing Then

                _fileWriter.WriteLine(rawLine)

            End If

        End Sub

 

        Public Sub EndWrite()

           

            If _fileWriter IsNot Nothing Then

                _fileWriter.Flush()

                _fileWriter.Close()

                _outFile.Close()

            End If

            _SafeFileHandle.Close()

            _SafeFileHandle.Dispose()

 

        End Sub

#End Region

 

    End Class

Answer 1

Hi,

You might have better luck getting this question answered in one of the other forums, as this one primarily deals with the Pos .Net library, which you don't appear to be using.

Alternatively, you could change your code to use Pos .Net instead, but I understand the Zebra service objects don't work very well with Pos .Net at the moment so you may be better off trying to fix what you have.

Answer 2

Hey Yort,
I am disappointed a bit. Because i am in a critical situation for this issue as i am not getting any solution for this problem. Can you let me know which forum can i post the same to get a better answer.

Thanks,
Palash

Answer 3

Hi,

I can understand that, but as I said, this forum is for the Pos .Net library which insulates developers from any port related work. As a result, devs using Pos .Net do not need to use the file API's, usb sub-system, serial ports etc. directly, and probably won't know enough to help unless they've worked with these things in some other capacity.

I would suggest the Visual C# General forum, it's not a language or BCL issue since it involves the Win32 API and so I would guess that is the most appropriate place. It also has a large number of devs who know a variety of topics, so there's a much better chance someone there can help.

Good luck !

Answer 4

Hi

i saw your one of the old question.. and now i have also  the same error in my visual studio project.

if u got any solution for the same . please share to me. 

error "Invalid Parameter : Name handle" in the line outFile = New FileStream(_SafeFileHandle, FileAccess.Write) 

thanks.......

Answer 5

Hi

Please post a new question on the new Microsoft Q&A forum

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Regards Les, Livingston, Scotland