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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