Visual Basic - Converting 3.0 to 6.0

Converting Visual Basic 3.0 to 6.0

Trying to convert a working application from VB 3.0 to VB 6.0 is one of the biggest mistakes I have made. Basically, the languages are different. The converted application runs more than a thousand times slower! (For real!!)

Loading VB 6.0 requires that you load IE 4.72 which I did not want (but its ok to use). Some VB 6.0 programs that you write require that you distribute IE 4.72, otherwise, your programs won't work.

When importing a project from VB 3.0 to Visual Basic 6.0, some things are lost.

ActiveX Controls - The following error message is common
I clicked yes, and the following was displayed
The same thing happened with anibtn32.ocx, guage32.ocx, graph32.ocx, keysta32.ocx, msoutl32.ocx, spin32.ocx, threed32.ocx. These errors were summarized in *.log.
Crystal ???? Probably Crystal Reports, probably deleted.
Common Dialog controls (Open, Save, SaveAs, Print ... - all implemented via CommDlg.dll) are all deleted and your custom code becomes worthless.
The classes SSPanel (ButtonBar_UIPanel3D2) and SSCommand (Capture_UIButton) were not loaded. These objects were configured as picture objects instead. As a result, many of the properties were no longer valid.
Basically, all VB 3.0 pre-defined symbolic constants must be replaced with their new VB 6.0 values. This includes keyboard definitions, colors, common control options, and everything else you can think of.

Screen.ActiveForm

Screen.ActiveForm no longer works during Form_Load() time. (I didn't check it else where.) Now you must use
Set MainForm = Forms(0)
instead of
Set MainForm = Screen.ActiveForm

Automatic Variant Conversion

The automatic conversion of a variant to a string has changed. Using
   Dim ErrorCount     ' This defines a variant
   ErrorCount = 5     ' Assign it a numerical value
Now you must use
   object.Text = "There are " & ErrorCount & " differences"
instead of
   object.Text = "There are " + ErrorCount + " differences"

Sizing Objects

The routines I used to automatically set the size of the pictureBox no longer give the correct size. The following code produces a rectangle 80 characters wide and 25 characters high in VB 3.0 and 79 characters wide and 24.5 characters high in VB 6.0.

  MainForm.Compare_Display_UIPicture.FontSize = Size
  
    ' Determine the height and width of a typical character
  H1 = MainForm.Compare_Display_UIPicture.TextHeight("A")
  W1 = MainForm.Compare_Display_UIPicture.TextWidth("A")

  MainForm.Compare_Display_UIPicture.Width = 80 * W1
  MainForm.Compare_Display_UIPicture.Height = 25 * H1

Re-sizing the form requires knowing information which is not available. When internal objects are located at 0,0, you need to know that 0,0 is really 40,300 or what ever. (This may be my error, the object was not at 0,0 but I thought it was.)

User Interface

When selecting text, when complete rows are selected, the cursor stops in the middle of the row. In VB 3.0, it selects entire rows.

Use the Object Browser to determine the methods and properties of objects.

VB has 34 base classes. Of these, 20 are UI controls, 7 are defined in Global (App, Clipboard, Forms, Licenses, Printer, Printers, Screen). The others are Form, MDIForm, Menu, PropertyPage, UserControl, UserDocument, VBControlExtender.

DoEvents

DoEvents hangs VB 6.0, works perfect in VB 3.0.

The PushKeys command is available for VB 5.0 and above only. This is the only reason I moved from VB 3.0 to VB 6.0. PushKeys works more than 100 times faster than the VB SendKeys command. However, the keystrokes appear to be queued until a DoEvents command is executed. Normally, this would not be a problem except that DoEvents stops the execution of the VB 6.0 application.

  formSave = Screen.ActiveForm.Caption
  AppActivate DOSAppName$     ' Transfers control to the DOS application
  PushKeys DOS_ScreenCapture$ ' Send keys to the active (DOS) application
  
    ' The following 4 lines of code are not needed in VB 3.0,
    ' These are needed so that the clipboard will be available
  For i = 1 To 10       ' I tried various values - 1, 10, 1000 - 
                        ' 1 failed, 10 work sometimes, 1000 hung
   DoEvents             ' Without this - Error - Can't Open Clipboard
  Next i
  AppActivate formSave  ' Without this, DoEvents hangs the application

    ' The following code never fails in VB 3.0, is intermittent in VB 6.0
  tt$ = Clipboard.GetText()

According to Microsoft, DoEvents returns control to the Visual Basic program after the operating system has finished processing the events in its queue and all keys in the SendKeys queue have been sent. The Sleep 32-bit API function is a subset of the DoEvents function.

When capturing the DOS screen using sendKeys, it is at least one thousand times slower than before (VB 3.0 is much faster than VB 6.0). Even the mouse hangs until to action is complete.

Program Directories

I tried to develop a template in one directory and do a save as in another directory. I ended up modifying the wrong data and lost the template. There is no way to modify the directory where project members are saved except to delete and reload them. I have not yet figured out how to determine where exe's are created.

Line Continuation

What a concept - starting with VB 4.0, a single command no longer has to be typed on single line. This is particularly important when defining or calling functions with lots of parameters.

In order to continue a command on the next line, terminate the line with a space, underscore, enter. Both of the following should give the same result

   Dim Msg   ' Declare variable
   Msg = "1st part of string "
   Msg = Msg & "Next part of string "
   Msg = Msg & "Last part of string"

   Msg = "1st part of string " _
         & "Next part of string " _
         & "Last part of string"

Common Dialog Controls

When converting from VB 3.0 to VB 6.0, the common dialog controls changed.

The conversion drops all common dialog controls from your application.
You must manually add ComDlg32.OCX ActiveX control to each application. In VB 3.0, CommDlg.dll was accessed via cmdialog.vbx The VB 6.0 help says to use CommDlg.dll, but the detailed instructions which explain how to make the connection do not work.

The constants changed. The VB 3.0 command

   CMDialog.Flags = OFN_FILEMUSTEXIST + OFN_HIDEREADONLY

no longer hides the readonly checkbox. Instead, you must use

   CMDialog.Flags = cdlOFNFileMustExist + cdlOFNHideReadOnly

Basically, all VB 3.0 constants must be replaced with their new VB 6.0 values.

Author: Robert Clemenzi - clemenzi@cpcug.org