How to let parent control know that its child got focus?

imagine that I have a Form with 9 controls (TabbedStuffControl) in a 3x3 tile, and these controls contain TabControls containing another control (StuffControl) with ListBoxes and TextBoxes.

I'd like to know a proper way to let TabbedStuffControl that its child has received a focus? e.g. user clicks into a textbox of StuffControl or drags something to listbox of StuffControl. Eventually the Form should know which TabbedStuffControl is active

Do I need to hook up GotFocus event of TextBoxes and ListBoxes and TabControls, then dispatch another event to finally let Form know who got focus? I think that there should be a simpler way - 开发者_运维知识库that somehow TabbedStuffControl knows that its child got focus, so there would be only one place in code that I'll hook up.

Thanks.

Using the Enter event (better then GotFocus) is certainly a good approach. Subscribe a handler for all controls, then go find the parent of the control in the Enter event handler. This sample code demonstrates the approach:

  public partial class Form1 : Form {
    public Form1() {
      InitializeComponent();
      wireEnter(this.Controls);
    }
    private void wireEnter(Control.ControlCollection ctls) {
      // Hook Enter event for all controls
      foreach (Control ctl in ctls) {
        ctl.Enter += ctl_Enter;
        wireEnter(ctl.Controls);
      }
    }

    TabbedStuffControl mParent;

    private void ctl_Enter(object sender, EventArgs e) {
      // Find parent
      Control parent = (sender as Control).Parent;
      while (parent != null && !(parent is TabbedStuffControl)) parent = parent.Parent;
      if (parent != mParent) {
        // Parent changed, do something.  Watch out for null
        //....
        mParent = parent as TabbedStuffControl;
      }
    }
  }

You'll have to use COM:

// Import GetFocus() from user32.dll
[DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.Winapi)]
internal static extern IntPtr GetFocus();

protected Control FocusControl
{
    get
    {
        Control focusControl = null;
        IntPtr focusHandle = GetFocus();

        if (focusHandle != IntPtr.Zero)
            // returns null if handle is not to a .NET control
            focusControl = Control.FromHandle(focusHandle);

        return focusControl;
    }
}