How to prevent closing of docked window?

Closing of docked window can be restricted using DockVisibilityChanging event. When the end users tries to change the docking control visibility, this event will be handled. The members of this event is as follows.

Members Description
Cancel This property gets/sets the value indicating whether the event should be canceled.
Control Gets the control which is undergoing the transfer. 
private void dockingManager1_DockVisibilityChanging(object sender, Syncfusion.Windows.Forms.Tools.DockVisibilityChangingEventArgs arg)

{

     arg.Cancel = true;

}
Private Sub dockingManager1_DockVisibilityChanging(ByVal sender As Object, ByVal arg As Syncfusion.Windows.Forms.Tools.DockVisibilityChangingEventArgs) Handles dockingManager1.DockVisibilityChanging

     arg.Cancel = True

End Sub

Additionally, the dock visibility of a control can be retrieved using GetDockVisibility method by passing the control as the parameter. Also DockVisibility can be set for the controls using SetDockVisibility method.