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Use UNC Names to Refer to Network Drives

Use UNC Names to Refer to Network Drives

If you write programs that access information on a network server, you never want to hard-code drive letters. Not all software vendors take advantage of the Uniform Naming Convention (UNC) (for example, \SERVERVOLUME ) technology. Use these API declarations:

 Public Declare Function GetVolumeInformation _	Lib "kernel32" Alias "GetVolumeInformationA" ( _	ByVal lpRootPathName As String, _	ByVal lpVolumeNameBuffer As String, _	ByVal nVolumeNameSize As Long, _	lpVolumeSerialNumber As Long, _	lpMaximumComponentLength As Long, _	lpFileSystemFlags As Long, _	ByVal lpFileSystemNameBuffer As String, _	ByVal nFileSystemNameSize As Long) As LongPublic Function GetNetworkDrive(FileSystem _	As String, VolumeName As String) As String	'Returns the first mapped drive letter 	'if successful or "NODRIVE" if fails.	'FileSystem and SysName refer to the 	'Network file system type: 	'NWCOMPA	=> Novell	'NTFS	=> Microsoft	'FAT		=> LocalMicrosoft	Dim SerialNum As Long, SysFlags As Long	Dim retVal As Long, Complength As Long	Dim VolBuff As String * 255, SysName As String * 255	Dim DrivePath As String	Dim i As Integer	GetNetworkDrive = "NODRIVE"	For i = 70 To 90		DrivePath = Chr(i) & ":"		retVal = GetVolumeInformation _			(DrivePath, VolBuff, 255, _			SerialNum, Complength, SysFlags, SysName, 255)		If (Mid$(VolBuff, 1, Len(VolumeName)) _			= UCase$(VolumeName)) And(Mid$(SysName,1, Len _			(FileSystem)) = FileSystem) Then				GetNetworkDrive = DrivePath				Exit For		End If	Next iEnd Function

Here’s the wrong and right ways to refer to network drives:

 Option ExplicitPublic Sub OpenDatabase()	'The Wrong Way!	Dim filespec as String	filespec = "H:PUBLICAPPSBTRIEVEMYDB.RDB"	'Some third-party control that opens the 	'database file.	...	...	... End SubPublic Sub OpenDatabase()	'A Better Way!	Dim filespec as String	Dim Vol1Drive As String	Vol1Drive = GetNetworkDrive("NWCOMPA","VOL1")	If Vol1Drive = "NODRIVE" Then 		MsgBox "Unable to open database. " & _			"The user does not have a " & _			"drive letter mapped to VOL1" 	Else		filespec = Vol1Drive & _			"PUBLICAPPSBTRIEVEMYDB.RDB"		'Some third-party control that opens 		'the database file. 		...		... 		...	End IfEnd Sub
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