How to stop Tab navigation on wpf window on custom validations.

Question

Hi everyone

I have a requirement .I have a wpf form and having 4 text boxes for that i have st the TabIndex as (0,1,2,3) And i can do tab navigation.

Now the requirement is

i have a validation on the textbox4 (on the EditModeEnded or LostFocus event of textbox control i am doing a validation if value is not correct i display a messagebox)

Now the problem is if the value is wrong an errorMessagebox is displayed .But if i click yes on the messagebox Button the tab is navigationg to the next control.(for my case to the next window.)

I need to control this behaviour .that means if validation fails i need to stop the tab navigation and bring the focus to the same text box.

please suggest a solution

Note: I have used textBox.MoveFocus to previous and textbox.focus() etc.None works

Thanks SNA