INFO: How Visual Basic 4.0 Handles Files Marked Read-Only (143044)

MORE INFORMATION

Example

1. Start a new project.
2. Remove the default Form1.
3. Add a reference to "Microsoft Visual Basic 4.0 Development Environment" using the Tools/References dialog.
4. Add a new standard module (Module1.BAS by default).
5. Put the following code in the standard module:

         ''' 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 not.
   
            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
   
         ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
   						

6. Add a new class module to the project (Class1.CLS by default.)
7. Set the following properties of the class module to the specified values:

         Property        Value
         ---------------------------------------
   
         Instancing      1 - Creatable MultiUse
         Name            Switch
         Public          True
   						

8. Put the following code in the class module:

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

9. Set the following Project Options:

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

10. Save the project.
11. Run the project.
12. Start up a second instance of Visual Basic (Form1 is created by default.)
13. Use the Add-In Manager to add the ReadOnlyMode.Switch add-in.
14. Open a code module with that has the read-only attribute set. You can tell if a file is marked read-only by the small red lock that appears in the project window next to the file.
15. From the Add-In menu you can switch the ReadOnlyMode. When checked the environment will be in strict mode and when unchecked it will be in lenient mode.