Question

我正在使用ZPL文件，首先我复制一份原件，在新版本中做一些更改，然后将文件发送到zebra打印机，最后我想删除该文件。

除了删除文件外，一切都很完美，我得到The process cannot access the file 'c:\test\Test.lbl' because it is being used by another process.

如何在发送到打印机后删除文件？

以下是代码：

Private Sub TextBox1_Validating(ByVal sender As System.Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles TextBox1.Validating
    Dim OrigFileName As String = "C:\Test\9320\089.lbl"
    Dim DestFileName As String = "c:\test\Test.lbl"
    Dim PrinterPath As String = "ZDesigner 110Xi4 600 dpi"

    Try
        File.Copy(OrigFileName, DestFileName)

        File.WriteAllText(DestFileName, File.ReadAllText(DestFileName).Replace("*(A)", TextBox1.Text.Trim()))
        File.WriteAllText(DestFileName, File.ReadAllText(DestFileName).Replace("*(B)", "1111111"))
        File.WriteAllText(DestFileName, File.ReadAllText(DestFileName).Replace("*(C)", "222222"))
        File.WriteAllText(DestFileName, File.ReadAllText(DestFileName).Replace("*(D)", "USA 6"))            

        ' Print the file to the printer.
        RawPrinterHelper.SendFileToPrinter(PrinterPath, DestFileName)

    Catch ex As Exception
        MessageBox.Show("Error: " & ex.Message)
    Finally
        File.Delete(DestFileName)
    End Try

End Sub

以下是来自http://support.microsoft.com/kb/322090

的RawPrinterHelper代码

Public Class RawPrinterHelper
' Structure and API declarions:
<StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Unicode)> _
Structure DOCINFOW
    <MarshalAs(UnmanagedType.LPWStr)> Public pDocName As String
    <MarshalAs(UnmanagedType.LPWStr)> Public pOutputFile As String
    <MarshalAs(UnmanagedType.LPWStr)> Public pDataType As String
End Structure

<DllImport("winspool.Drv", EntryPoint:="OpenPrinterW", _
   SetLastError:=True, CharSet:=CharSet.Unicode, _
   ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function OpenPrinter(ByVal src As String, ByRef hPrinter As IntPtr, ByVal pd As Long) As Boolean
End Function
<DllImport("winspool.Drv", EntryPoint:="ClosePrinter", _
   SetLastError:=True, CharSet:=CharSet.Unicode, _
   ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function ClosePrinter(ByVal hPrinter As IntPtr) As Boolean
End Function
<DllImport("winspool.Drv", EntryPoint:="StartDocPrinterW", _
   SetLastError:=True, CharSet:=CharSet.Unicode, _
   ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function StartDocPrinter(ByVal hPrinter As IntPtr, ByVal level As Int32, ByRef pDI As DOCINFOW) As Boolean
End Function
<DllImport("winspool.Drv", EntryPoint:="EndDocPrinter", _
   SetLastError:=True, CharSet:=CharSet.Unicode, _
   ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function EndDocPrinter(ByVal hPrinter As IntPtr) As Boolean
End Function
<DllImport("winspool.Drv", EntryPoint:="StartPagePrinter", _
   SetLastError:=True, CharSet:=CharSet.Unicode, _
   ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function StartPagePrinter(ByVal hPrinter As IntPtr) As Boolean
End Function
<DllImport("winspool.Drv", EntryPoint:="EndPagePrinter", _
   SetLastError:=True, CharSet:=CharSet.Unicode, _
   ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function EndPagePrinter(ByVal hPrinter As IntPtr) As Boolean
End Function
<DllImport("winspool.Drv", EntryPoint:="WritePrinter", _
   SetLastError:=True, CharSet:=CharSet.Unicode, _
   ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function WritePrinter(ByVal hPrinter As IntPtr, ByVal pBytes As IntPtr, ByVal dwCount As Int32, ByRef dwWritten As Int32) As Boolean
End Function

' SendBytesToPrinter()
' When the function is given a printer name and an unmanaged array of  
' bytes, the function sends those bytes to the print queue.
' Returns True on success or False on failure.
Public Shared Function SendBytesToPrinter(ByVal szPrinterName As String, ByVal pBytes As IntPtr, ByVal dwCount As Int32) As Boolean
    Dim hPrinter As IntPtr      ' The printer handle.
    Dim dwError As Int32        ' Last error - in case there was trouble.
    Dim di As DOCINFOW          ' Describes your document (name, port, data type).
    Dim dwWritten As Int32      ' The number of bytes written by WritePrinter().
    Dim bSuccess As Boolean     ' Your success code.

    ' Set up the DOCINFO structure.
    With di
        .pDocName = "My Visual Basic .NET RAW Document"
        .pDataType = "RAW"
    End With
    ' Assume failure unless you specifically succeed.
    bSuccess = False
    If OpenPrinter(szPrinterName, hPrinter, 0) Then
        If StartDocPrinter(hPrinter, 1, di) Then
            If StartPagePrinter(hPrinter) Then
                ' Write your printer-specific bytes to the printer.
                bSuccess = WritePrinter(hPrinter, pBytes, dwCount, dwWritten)
                EndPagePrinter(hPrinter)
            End If
            EndDocPrinter(hPrinter)
        End If
        ClosePrinter(hPrinter)
    End If
    ' If you did not succeed, GetLastError may give more information
    ' about why not.
    If bSuccess = False Then
        dwError = Marshal.GetLastWin32Error()
    End If
    Return bSuccess
End Function ' SendBytesToPrinter()

' SendFileToPrinter()
' When the function is given a file name and a printer name, 
' the function reads the contents of the file and sends the
' contents to the printer.
' Presumes that the file contains printer-ready data.
' Shows how to use the SendBytesToPrinter function.
' Returns True on success or False on failure.
Public Shared Function SendFileToPrinter(ByVal szPrinterName As String, ByVal szFileName As String) As Boolean
    ' Open the file.
    Dim fs As New FileStream(szFileName, FileMode.Open)
    ' Create a BinaryReader on the file.
    Dim br As New BinaryReader(fs)
    ' Dim an array of bytes large enough to hold the file's contents.
    Dim bytes(fs.Length) As Byte
    Dim bSuccess As Boolean
    ' Your unmanaged pointer.
    Dim pUnmanagedBytes As IntPtr

    ' Read the contents of the file into the array.
    bytes = br.ReadBytes(fs.Length)
    ' Allocate some unmanaged memory for those bytes.
    pUnmanagedBytes = Marshal.AllocCoTaskMem(fs.Length)
    ' Copy the managed byte array into the unmanaged array.
    Marshal.Copy(bytes, 0, pUnmanagedBytes, fs.Length)
    ' Send the unmanaged bytes to the printer.
    bSuccess = SendBytesToPrinter(szPrinterName, pUnmanagedBytes, fs.Length)
    ' Free the unmanaged memory that you allocated earlier.
    Marshal.FreeCoTaskMem(pUnmanagedBytes)
    Return bSuccess
End Function ' SendFileToPrinter()

' When the function is given a string and a printer name,
' the function sends the string to the printer as raw bytes.
Public Shared Function SendStringToPrinter(ByVal szPrinterName As String, ByVal szString As String)
    Dim pBytes As IntPtr
    Dim dwCount As Int32
    ' How many characters are in the string?
    dwCount = szString.Length()
    ' Assume that the printer is expecting ANSI text, and then convert
    ' the string to ANSI text.
    pBytes = Marshal.StringToCoTaskMemAnsi(szString)
    ' Send the converted ANSI string to the printer.
    SendBytesToPrinter(szPrinterName, pBytes, dwCount)
    Marshal.FreeCoTaskMem(pBytes)
End Function

结束班

Answer 1

在SendFileToPrinter()中我将函数的结尾更改为此，它实际上会在使用后忘记关闭BinaryReader;

Marshal.FreeCoTaskMem(pUnmanagedBytes)
br.Close()                                    ' <--- Close the BinaryReader
Return bSuccess
End Function                                  ' SendFileToPrinter()

使用vb.net发送到打印机后删除文件

1 个答案: