Hi,

   I got a very strange problem. Please do followings

1. Create Form1, Form2, Form3
2. Make Form1 as a MDI Parent while Form2 and Form3 are mdichild, and put
two buttons, button1 and button2, on Form1
3. button1 will open Form2, and button2 will open Form3
4. Put a TextBox in Form3
5. Put Debug.WriteLine("Test") in Validating event of Textbox mentioned in
step4
6. Let's run this app, starting with Form1
7. Open Form2, and Form3 as mdichild Forms.
8. Make TextBox in Form3 have focus, then Tab off this control we should see
one line in output window.    ...Test....
9  Make TextBox in Form3 have focus ---------- This is very important
10. Let's use Ctrl-Tab to switch to Form2, then switch back to Form3.
11. TextBox should still have focus.
12. Then modify something in the TextBox on Form3
13. Please tab off.  This time, Validating event is not fired up !!!!!! why
?

    This happens to me everytime. Do I miss something ? Or this is a bug ?

    Thanks ! Please help me out on this problem

Fei