Microsoft KB Archive/176392

= FIX: Can't Assign an Object to an ActiveX Tag Property =

Article ID: 176392

Article Last Modified on 11/18/2003

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APPLIES TO


 * Microsoft Visual Basic 5.0 Control Creation Edition
 * Microsoft Visual Basic 5.0 Professional Edition
 * Microsoft Visual Basic 5.0 Enterprise Edition

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This article was previously published under Q176392



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
 Create a new Standard EXE Project. Form1 is created by default. From the Project menu, select Components. In the Controls Tab of the Components dialog box, make sure that the Microsoft Windows Common Controls 5.0 is checked. Click OK to Close the Components dialog box. Add a TreeView Control, Text Box, and three CommandButtons to Form1.  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

</li> Save the project.</li> 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.</li></ol>

Keywords: kbbug kbfix kbvbp600fix kbctrl KB176392

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