FIX: ParentControls.Count May Fail on Windows NT 4, Service Pack 4 (223104)


The information in this article applies to:

  • Microsoft Visual Basic Learning Edition for Windows 6.0
  • Microsoft Visual Basic Professional Edition for Windows 6.0
  • Microsoft Visual Basic Enterprise Edition for Windows 6.0
This article was previously published under Q223104

SYMPTOMS

Under Windows NT Service Pack 4, if a Usercontrol accesses the ParentControls.Count property and there are 32 or more controls on the form, including the Usercontrol and any controls on the Usercontrol, the Visual Basic app might crash.

NOTE: This bug does not occur on Windows NT 4.0 Service Pack 5 or on Windows 2000 machines.

CAUSE

This is caused by an error in Visual Basic's heap allocation mechanism.

STATUS

Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article.

This bug was corrected in Visual Studio 6.0 Service Pack 3.

For more information about Visual Studio 6.0 Service Packs, please see the following articles in the Microsoft Knowledge Base:


194022 INFO: Visual Studio 6.0 Service Packs, What, Where, Why

194295 HOWTO: Tell That Visual Studio 6.0 Service Packs Are Installed

MORE INFORMATION

Steps to Reproduce Behavior

  1. Create a new Standard EXE project in Visual Basic 6.0. Form1 is created by default.
  2. Click Add Project on the File menu and add a new ActiveX Control project. UserControl1 is created by default.
  3. Add a CommandButton to the UserControl.
  4. Place the following code in the Click event of the CommandButton:
    MsgBox UserControl.ParentControls.Count
  5. Close the designer window for UserControl1.
  6. Place a UserControl1 control on Form1 of the Standard EXE Project.
  7. Add 30 TextBox controls to Form1 of the Standard EXE project.
  8. Press the F5 key to run the project.
  9. Click the CommandButton of the UserControl.
After clicking the button in the last step, an Application Error occurs in VB6.exe.

REFERENCES

For additional information, please see the following articles in the Microsoft Knowledge Base:

195009 Application Access Violation or Hang After Applying SP4

219278 BUG: OLAP MDX Application Gives Application Error in VB IDE
Modification Type:MajorLast Reviewed:5/13/2003
Keywords:kbBug kbfix kbVS600sp3fix KB223104 kbAudDeveloper
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