我在服务器上有一个excel文件位置。
我正在使用VB.NET编写的应用程序以只读模式打开文件。
用户1以只读模式打开文件。 用户2如何检测该文件是否处于打开状态?
谢谢, 一个
答案 0 :(得分:1)
第二个用户可以尝试以读写模式打开文件,以了解文件是否正在使用。
答案 1 :(得分:1)
如果文件是ReadOnly状态,则需要测试文件只读,因为ReadWrite将失败。 以下是一些方法。不知道除了Randy Birch的最后一个,我从哪里得到了它们。 速度测试支持FileIsOpen3和FileIsOpen4。
Function FileIsOpen1(ByVal pathfile As String) As Boolean
Dim ff As Integer
If System.IO.File.Exists(pathfile) Then
Try
ff = FreeFile()
Microsoft.VisualBasic.FileOpen(ff, pathfile, OpenMode.Binary, OpenAccess.Read, OpenShare.LockReadWrite)
Return False
Catch
Return True
Finally
FileClose(ff)
End Try
Return True
End If
End Function
Function FileIsOpen2(ByVal pathfile As String) As Boolean
Dim stream As FileStream = Nothing
Dim fi As FileInfo = Nothing
If System.IO.File.Exists(pathfile) Then
Try
fi = New System.IO.FileInfo(pathfile)
stream = fi.Open(FileMode.Open, FileAccess.Read, FileShare.None)
Return True
Catch generatedExceptionName As IOException
Return False
Finally
If stream IsNot Nothing Then
stream.Close()
End If
fi = Nothing
End Try
Return True
End If
End Function
Private Function FileIsOpen3(ByVal pathfile As String) As Boolean
Try
Dim fs As IO.FileStream = IO.File.Open(pathfile, IO.FileMode.Open, IO.FileAccess.Read, IO.FileShare.None)
fs.Close()
fs.Dispose()
fs = Nothing
Return False
Catch ex As IO.IOException ' File open
Return True
Catch ex As Exception ' Unknown error
Return True
End Try
End Function
Private Declare Function CreateFile Lib "kernel32" _
Alias "CreateFileA" _
(ByVal lpFileName As String, _
ByVal dwDesiredAccess As Long, _
ByVal dwShareMode As Long, _
ByVal lpSecurityAttributes As Long, _
ByVal dwCreationDisposition As Long, _
ByVal dwFlagsAndAttributes As Long, _
ByVal hTemplateFile As Long) As Long
Private Declare Function CloseHandle Lib "kernel32" _
(ByVal hFile As Long) As Long
' Method
Shared Function FileIsOpen4(ByVal pathfile As String) As Boolean
' Is File In Use ©1996-2009 Randy Birch
' http://vbnet.mvps.org/index.html?code/fileapi/createfile_inuse.htm
Const GENERIC_READ As Long = &H80000000
Const INVALID_HANDLE_VALUE As Long = -1
Const OPEN_EXISTING As Long = 3
Const FILE_ATTRIBUTE_NORMAL As Long = &H80
Dim hFile As Long
If System.IO.File.Exists(pathfile) Then
Try
' note that FILE_ATTRIBUTE_NORMAL (&H80) has a different value than VB's constant vbNormal (0)!
hFile = CreateFile(pathfile, GENERIC_READ, 0, 0, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0&)
' this will evaluate to either -1 (File in use) or 0 (File free)
Return hFile = INVALID_HANDLE_VALUE
Catch ex As Exception
MessageBox.Show(ex.ToString)
Finally
CloseHandle(hFile)
End Try
Else
Return True
End If
End Function