如何避免Access数据库系统在一台电脑被多次重复打开（Multiple instances of accde file）

总结国外论坛 access-programmers的一篇文章。因为平台不允许发链接，所以大家直接用 Multiple instances of accde file 搜索这篇原文。技巧来自几位不同的作者。

一共有4种方法来实现，推荐最后面2种方法

方法一、创建一个本地lock文件来判断有否多次打开

Option Compare Database

Option Explicit

Function IsDatabaseAlreadyOpen() As Boolean

    ' Check if the lock file exists

    Dim lockFilePath As String

    lockFilePath = CurrentProject.Path & "database.lock"

    If Dir(lockFilePath) <> "" Then

        IsDatabaseAlreadyOpen = True

    Else

        IsDatabaseAlreadyOpen = False

    End If

End Function

Sub CreateLockFile()

    ' Create the lock file

    Dim lockFilePath As String

    lockFilePath = CurrentProject.Path & "database.lock"

    Dim lockFileNumber As Integer

    lockFileNumber = FreeFile()

    Open lockFilePath For Output As lockFileNumber

    Close lockFileNumber

End Sub

Sub DeleteLockFile()

    ' Delete the lock file

    Dim lockFilePath As String

    lockFilePath = CurrentProject.Path & "database.lock"

    If Dir(lockFilePath) <> "" Then

        Kill lockFilePath

    End If

End Sub

Private Sub Form_Load()

    ' Check if the database is already open

    If IsDatabaseAlreadyOpen() Then

        MsgBox "The database is already open.", vbInformation

        DoCmd.Close acForm, Me.Name

    Else

        ' Create the lock file

        CreateLockFile

        Me.cboPartNumber.Locked = False

        Me.cboPartNumber.BackColor = 16777215

        Debug.Print "Clearing Image"

        Me.Image0.Picture = ""

    End If

End Sub

Private Sub Form_Unload(Cancel As Integer)

    ' Delete the lock file when the form is closed

    DeleteLockFile

End Sub

方法二、判断Access自身的临时文件

If Len(currentproject.Path & "database.laccdb")>0 Then

   DoCmd.Quit

End If

方法三、使用Access命令行参数独占打开

如果您可以让用户通过链接(或者批处理文件)打开数据库，您可以使用Microsoft Access命令行开关“/excl”。

这将打开Access数据库进行独占访问。

一旦数据库以这种方式打开，用户就不能再次打开它，无论他尝试哪种方式，直到独占会话被关闭。

信息:如果Microsoft Access以独占方式打开数据库，则根本不会生成锁定文件。

方法四、使用winmgmts 判断进程数

我最终使用了下面的代码，这是我从几个地方搜集来的。再次感谢所有的反馈。

代码:

Function CountProcessInstances(process As String) As Integer

    Dim objList As Object

    Dim count As Integer

    Set objList = GetObject("winmgmts:") _

        .ExecQuery("select * from win32_process where name='" & process & "'")

    count = objList.count

    CountProcessInstances = count

End Function

Sub IsProcessRunning()

    Dim processName As String

    Dim processCount As Integer

    ' Checks if msaccess.exe is running

    processName = "msaccess.EXE"

    processCount = CountProcessInstances(processName)

    ' Checks if there are more than one instance of msaccess.exe running

    If processCount > 1 Then

        'MsgBox "The process " & processName & " is already running " & processCount & " times. Please close one of the instances before continuing.", vbExclamation

        MsgBox "The Database is already open. Please close one of the instances before continuing.", vbExclamation

        Application.Quit

    End If

End Sub

使用的解决方案是检查Access程序的多个实例，而不是特定数据库应用程序(ACCDE)的多个实例

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