problem focusing a form

Question

Hi,
C#. .Net 4.0
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I've difficulties focusing a form. This is the scenario :

MDI application, Child forms are shown tabbed, like Firefox or IE8 tabs.

From one MDIchild form (MDIchild1) I open a dialog form (dialog1), from dialog1 I call a helper method (in Helper library) to create and show an MDIchild

form (MDIchild2), then close dialog1.

Everything is OK, except that the keyboard input goes to MDIchild1, though MDIchild2 is the one that has the focus.

And I want the keyboard input goes to MDIchild2.

NB. The MDiContainer form shows that MDIchild2 is the active child form.