This article was previously published under Q312120
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When you place an ActiveX control that was created in Visual Basic 6.0 or Visual C++ 6.0 on a form in a Visual Studio .NET Windows application, the control may disappear from the form in the design view. The control disappears when you use the Properties window to set the value of a form property, such as ShowInTaskBar.
If you set any property of the form (such as ShowInTaskBar), the form's handle is recreated. Some ActiveX controls hide their windows when the parent's Hwnd gets a WM_DESTROY message. This sets the control's STATE_VISIBLE property to false inside the property's state bits. When the form's handle is recreated, the control's handle is not recreated because the control's STATE_VISIBLE property is set to false.
To work around the problem, you can set the properties in the Form_Load event instead of in the Properties window.
Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article.
Steps to Reproduce the Behavior
Use Visual Basic 6.0 to create a UserControl, or use Visual C++ 6.0 to create an Active Template Library (ATL) or Microsoft Foundation Classes (MFC) control.
Register the control on the computer that has Visual Studio .NET installed.
Start Visual Studio .NET. Use Visual Basic .NET, Visual C# .NET, or Visual J# .NET to create a new Windows application. Form1 is created by default.
Right-click the Toolbox window, and then click Customize Toolbox on the shortcut menu.
Click the COM Components tab. Select the ActiveX control that you created in step 1 from the list. Click OK, and the control will appear in the Toolbox.
Add this control to Form1.
In the Properties window, change the value of the Form1 ShowInTaskBar property.
The ActiveX control disappears from the form immediately.