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Q176392: FIX: Can’t Assign an Object to an ActiveX Tag Property

Article: Q176392
Product(s): Microsoft Visual Basic for Windows
Version(s): 5.0
Operating System(s): 
Keyword(s): kbActiveX kbCtrl kbVBp kbVBp500bug kbVBp600fix kbGrpDSVB kbDSupport
Last Modified: 27-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Control Creation Edition for Windows, version 5.0 
- Microsoft Visual Basic Professional Edition for Windows, version 5.0 
- Microsoft Visual Basic Enterprise Edition for Windows, version 5.0 
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SYMPTOMS
========

When you attempt to set the Tag property of an object in the Comctl32.ocx
ActiveX Control, you will receive run-time error 424:

  "Object required"

The following examples cause the error:

     Set TabStrip1.Tabs(1).Tag = Text1
     Set Toolbar1.Buttons(1).Tag = Text1
     Set StatusBar1.Panels(1).Tag = Text1
     Set TreeView1.Nodes(1).Tag = Text1
     Set ListView1.ListItems(1).Tag = Text1
     Set ImageList1.ListImages(1).Tag = Text1

If you assign an object to one of these Tag properties without using the "Set"
statement, the default property of the object is correctly assigned to the Tag
property. For instance, the following examples result in the Text property of
Text1 being assigned to the Tag properties:

     TabStrip1.Tabs(1).Tag = Text1
     Toolbar1.Buttons(1).Tag = Text1
     StatusBar1.Panels(1).Tag = Text1
     TreeView1.Nodes(1).Tag = Text1
     ListView1.ListItems(1).Tag = Text1
     ImageList1.ListImages(1).Tag = Text1

If the object you are assigning to the Tag property with this method does not
have a default property, you correctly get error 438 "Object doesn't support
this property or method." The following examples would result in this error
because forms do not have default properties:

     TabStrip1.Tabs(1).Tag = Me
     Toolbar1.Buttons(1).Tag = Me
     StatusBar1.Panels(1).Tag = Me
     TreeView1.Nodes(1).Tag = Me
     ListView1.ListItems(1).Tag = Me
     ImageList1.ListImages(1).Tag = Me

If the object you are assigning to the Tag property with this method is un-
initialized, Visual Basic incorrectly attempts to navigate to the default
property, which causes a crash. The following examples will cause an
"Application error" under NT 4.0, or a "This Program has performed an illegal
operation" error under Windows 95, Windows 98, or Windows Me:

     Dim t As TextBox
     TabStrip1.Tabs(1).Tag = t
     Toolbar1.Buttons(1).Tag = t
     StatusBar1.Panels(1).Tag = t
     TreeView1.Nodes(1).Tag = t
     ListView1.ListItems(1).Tag = t
     ImageList1.ListImages(1).Tag = t

Similarly, setting the Tag property to "Nothing" causes the same crash.


STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This bug has been fixed in Visual Basic 6.0.

MORE INFORMATION
================

The online Help for the ActiveX Tag Property says the following:

  "The Tag property is of type Variant for ActiveX control collections such as
  Toolbar Button objects, TreeView Node objects, ListView ListItem and
  ColumnHeader objects, ImageList ListImage objects, TabStrip Tab objects, and
  StatusBar Panel objects. This is a powerful language feature that enables you
  to pass, for example, objects (such as a selected Node) as a Tag."

However, if you try to Set a Tag Property to an Object you will receive a
run-time error 424 "Object required." You can, however, assign an object to a
Tag Property and it will store the default property of the object to the Tag.
You cannot store the Object itself in the Tag Property.

Steps to Reproduce Behavior
---------------------------

1. Create a new Standard EXE Project. Form1 is created by default.

2. From the Project menu, select Components.

3. In the Controls Tab of the Components dialog box, make sure that the
  Microsoft Windows Common Controls 5.0 is checked.

4. Click OK to Close the Components dialog box.

5. Add a TreeView Control, Text Box, and three CommandButtons to Form1.

6. Add the following Code to Form1:

        'Start Code
        Private Sub Command1_Click()
           'try to set the Tag of a node to an Object
           ' This will give error number 424
           Set TreeView1.Nodes(1).Tag = Text1
        End Sub

        Private Sub Command2_Click()
           'This will store the default property of an object
           'to the Tag of a node
           TreeView1.Nodes(1).Tag = Text1
           Print "Nodes(1).Tag = " & TreeView1.Nodes(1).Tag
        End Sub

       Private Sub Command3_Click()
          'This will cause a crash
           Dim t As TextBox
          'Set t = Text1
          TreeView1.Nodes(1).Tag = t
          Debug.Print TreeView1.Nodes(1).Tag
       End Sub

        Private Sub Form_Load()
           ' Set Treeview control properties.
           TreeView1.LineStyle = tvwRootLines  ' Linestyle 1

           ' Add Node objects.
           Dim nodX As Node    ' Declare Node variable.
           ' First node with 'Root' as text.
           Set nodX = TreeView1.Nodes.Add(, , "r", "Root")

           ' This next node is a child of Node 1 ("Root").
           Set nodX = TreeView1.Nodes.Add("r", tvwChild, "child1", "Child")
        End Sub
        'End Code

7. Save the project.

8. Press the F5 key to run the project, and then Click Command1. You will get
  run-time error 424. If you Click Command2, you will see that the default
  property of your text box (Text1) is stored in the Tag property. If you click
  Command3, you will crash.

NOTE: In order for the code in the Command3_Click event to work properly after
the fix is applied, the comment must be removed from the line of code that
performs the Set operation.

Additional query words:

======================================================================
Keywords          : kbActiveX kbCtrl kbVBp kbVBp500bug kbVBp600fix kbGrpDSVB kbDSupport 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVBA500Search kbVBA500 kbVB500 kbZNotKeyword3
Version           : :5.0
Issue type        : kbbug
Solution Type     : kbfix

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