INFO: How Visual Basic 4.0 Handles Files Marked Read-Only

• Standard, Professional, and Enterprise Editions of Microsoft Visual Basic, 16-bit and 32-bit, for Windows, version 4.0
• Microsoft Visual SourceSafe for Windows, version 4.00

SUMMARY

Visual Basic 4.0 may handle files with the read-only attribute set differently than Visual Basic 3.0. This may result in a "Can't Edit Module" error when trying to change a code module. The Visual Basic 4.0 development environment will handle read-only files in one of two ways. The way Visual Basic 4.0 behaves is dependent on the current setting of the ReadOnlyMode property of the development environment. If the ReadOnlyMode is set to 0 (lenient) you will be able to edit files marked read-only just like Visual Basic 3.0. Of course you will still not be able to save your changes. If the ReadOnlyMode is set to 1 (strict) Visual Basic will not allow you to edit files marked read-only.

MORE INFORMATION

The default ReadOnlyMode for Visual Basic 4.0 is lenient. However, the default can be changed to strict by adding ReadOnlyMode=1 to the Visual Basic section of the VB.INI.

ReadOnlyMode can also be changed dynamically by Visual Basic 4.0 add-ins through the ReadOnlyMode property of the Application object of Visual Basic 4.0 add-in object model. The Microsoft SourceSafe add-in for Visual Basic 4.0 sets Visual Basic 4.0 to the strict mode. The following example shows you how to create a add-in that will allow you to toggle the ReadOnlyMode from a menu item.

Example

1. Start a new project.

   using the Tools/References dialog.

   ''' MODULE1.BAS
'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
   #If Win16 Then
      Declare Function WritePrivateProfileString Lib "KERNEL" ( _
         ByVal AppName As String, ByVal KeyName As String, _
         ByVal keydefault As String, ByVal FileName As String) As Integer
      Declare Function GetPrivateProfileString Lib "KERNEL" ( _
         ByVal AppName As String, ByVal KeyName As String, _
         ByVal keydefault As String, ByVal ReturnString As String, _
         ByVal NumBytes As Integer, ByVal FileName As String) As Integer
   #ElseIf Win32 Then
      Declare Function WritePrivateProfileString Lib "KERNEL32" _
         Alias "WritePrivateProfileStringA" (ByVal AppName As String, _
         ByVal KeyName As String, ByVal keydefault As String, _
         ByVal FileName As String) As Long
      Declare Function GetPrivateProfileString Lib "KERNEL32" _
         Alias "GetPrivateProfileStringA" (ByVal AppName As String, _
         ByVal KeyName As String, ByVal keydefault As String, _
         ByVal ReturnString As String, ByVal NumBytes As Long, _
         ByVal FileName As String) As Long
   #End If

   Sub Main()
      #If Win16 Then
         Const Section = "Add-Ins16"
      #ElseIf Win32 Then
         Const Section = "Add-Ins32"
      #End If
      Const BufSize = 255

      Dim Ret As Variant
      Dim RetStr As String

      'Check to see if the entry is already in the VB.INI file.  Add if

      RetStr = Space(BufSize)
      Ret = GetPrivateProfileString(Section, "ReadOnlyMode.Switch", _
         "NotFound", RetStr, BufSize, "VB.INI")
      RetStr = Left(RetStr, Ret)
      If RetStr = "NotFound" Then
         WritePrivateProfileString Section, "ReadOnlyMode.Switch", _
            "0", "VB.INI"
      End If
   End Sub

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

   values:

   Property        Value
   ----------      -----------------------

   Instancing      1 - Creatable MultiUse
   Name            Switch
   Public          True

   ''' CLASS1.CLS
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
   Option Explicit

   Private ThisInstance As VBIDE.Application
   Private AddInMenuLine As VBIDE.MenuLine
   Private AddInID As Long

   Public Sub ConnectAddIn(VBInstance As Object)
      Set ThisInstance = VBInstance
      Set AddInMenuLine = ThisInstance.AddInMenu.MenuItems.Add( _
         "Strict &ReadOnlyMode")
      AddInMenuLine.Checked = ThisInstance.ReadOnlyMode
      AddInID = AddInMenuLine.ConnectEvents(Me)
   End Sub

   Public Sub DisconnectAddIn(Mode As Integer)
      AddInMenuLine.DisconnectEvents AddInID
      ThisInstance.AddInMenu.MenuItems.Remove AddInMenuLine
   End Sub

   Public Sub AfterClick()
      ThisInstance.ReadOnlyMode = ThisInstance.ReadOnlyMode Xor 1
      AddInMenuLine.Checked = ThisInstance.ReadOnlyMode
   End Sub

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

   Option            Value
   --------------    ---------------------

   Startup Form      Sub Main
   Project Name      ReadOnlyMode
   StartMode         OLE Server
   Error Trapping    Break in Class Module