title: How track when any child control gets or loses the focus in WinForms?
body: <p>I have a Windows Forms custom control which acts like a panel in that it can contain any number of children. The number and type of the child controls are determined at runtime and so I need to work in a generic manner without knowing the exact child controls that might or might not be present.</p>
  
  <p>I want to alter the background color of my panel depending on if the panel contains the focus. So if a child of the panel (or a child of a child of the panel etc...) takes the focus I want to know this so I can update the background color of the custom panel. When the focus shifts away to something that is not in the child hierarchy then I also need to know so I can revert to the original background color.</p>
  
  <p>The Control.ContainsFocus is great for telling me if the panel contains the focus in the child hierarchy but I need to know when there is a change. At the moment I can only come up with the following poor mechanism. </p>
  
  <p>I hook into the GotFocus/LostFocus of each child and each child of each child etc. I also have to hook the ControlAdded/ControlRemoved to ensure I keep in sync with the possible changing child hieararchy. As you can see this might end up with ALOT of event hooks and I suspect there must be an easier approach. Any ideas?</p>