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Showing a hidden floating form with DockManager

Thread ID:





90902 Oct 23,2009 02:46 PM UTC Nov 3,2009 10:07 AM UTC WinForms 4
Tags: Tools
Mike Mann
Asked On October 23, 2009 02:46 PM UTC

I have run into a problem when attempting to show a floating form that has been hidden. I was under the impression that SetDockVisibility() was responsible for setting the visibility of floating controls as well as docked controls, however I am getting a NullReferenceException when calling SetDockVisibility() on a control that has been floated.

When the control is hidden by clicking the Close button in the upper right corner of the floating form and then I try to make the form visible again using SetDockVisibility(), the following exception is thrown:
System.NullReferenceException: Object reference not set to an instance of an object.
at Syncfusion.Windows.Forms.Tools.FloatingForm.UpdateFormBorderStyle()
at Syncfusion.Windows.Forms.Tools.FloatingForm.OnVisibleChanged(EventArgs e)
at System.Windows.Forms.Control.WmShowWindow(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
at System.Windows.Forms.ContainerControl.WndProc(Message& m)
at System.Windows.Forms.Form.WmShowWindow(Message& m)
at System.Windows.Forms.Form.WndProc(Message& m)
at Syncfusion.Windows.Forms.Tools.FloatingForm.WndProc(Message& msg)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

Is there a solution or work around for this? Is this even the proper way of making a floating form visible again after closing it?

I am using Syncfusion v7.3.0.20.
I have been using sample code provided by Syncfusion from an old forum post:

Mike Mann
Replied On October 23, 2009 02:49 PM UTC

Sorry, I forgot to include steps to reproduce in my first post.

1.) Start the sample
2.) Click the "Visiblity=true" button to make the panel visible.
3.) Drag the panel out of the form to make it float.
4.) Close the floating form by clicking the "X" in the upper right corner.
5.) Click the "Visiblity=true" button again to make the floating form visible again.

At this point the application should throw the exception and crash.

Mano J [Syncfusion]
Replied On October 27, 2009 09:42 AM UTC

Hi Mike,

It is a known issue in We have fixed this issue and this fix will be available in volume 4 release, scheduled to be released on first week of November.


Mike Mann
Replied On October 27, 2009 02:02 PM UTC

Would it be possible for you to provide us with a patch for this issue prior to the release of the next build?

Nandakumar R [Syncfusion]
Replied On November 3, 2009 10:07 AM UTC


Can you please create a DirectTrac incident under your account in DirectTrac and we will post a patch in the incident?

Thanks for your interest in Syncfusion Essential Studio.



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