How to loop through all controls in a Windows Forms form or how to find if a particular control is a container control?

Question

I will tell my requirement. I need to have a keydown event for each control in the Windows Forms form. It's better to do so rather than manually doing it for all controls if what I have to do for all keydown events is the same.

So I could basically do this:

foreach (Control c in this.Controls)
    c.KeyDown+= new KeyEventHandler(c_KeyDown);

But here, the foreach doesn't loop inside those controls which reside inside a groupBox or a tabControl. I mean if the form (this) contains a groupBox or some other container control, then I can get a keydown event for that particular container control. And the foreach doesn't loop through controls that reside inside that container control.

Question 1: How do I get a keydown event for "all" the controls in a form?

If the above puzzle is solved, then my problem is over.

This is what I can otherwise do:

Mainly pseudo code

foreach (Control c in this.Controls)
{
     c.KeyDown += new KeyEventHandler(c_KeyDown);

     if (c is Container control)
           FunctionWhichGeneratesKeyDownForAllItsChildControls(c)
}

I know I will have to go through FunctionWhichGeneratesKeyDownForAllItsChildControls(c) many times over to get keydown for all controls if there are groupboxes inside a groupbox or so. I can do it. My question is,

Question 2: How do I check if c is a container control?

Answer 1

A simple recursive function should do it.

private void AddEvent(Control parentCtrl)
{
  foreach (Control c in parentCtrl.Controls)
  {
    c.KeyDown += new KeyEventHandler(c_KeyDown);
    AddEvent(c);
  }
}