Control::TopLevelControl Property
Gets the parent control that is not parented by another Windows Forms control. Typically, this is the outermost Form that the control is contained in.
Assembly: System.Windows.Forms (in System.Windows.Forms.dll)
The top-level control is defined as the parent control that is not parented by another Windows Forms control. Typically, this is the outermost Form that the control is contained in. For example, if the control is contained on an MDI child Form, then the top-level control is the Multiple Document Interface (MDI) parent Form. If the control is not parented on a Form, this property will return null.
for all windows to get this property value. Associated enumeration: UIPermissionWindow::AllWindows
Available since 1.1