Focus Problem in TextBox

[Abhi]

Hi Team,
               If we use,
                                 txtbox.Focus();

                Normally, Focus will go to the partcular textbox (at that time, If we check in QuickWatch ,txtbox.Focus Value is true)

                In Some cases, Even though If I use,
                                                                            txtbox.Focus();
                focus is not coming to the textbox(at that time, If we check in QuickWatch, txtbox.Focus Value is False)
                
                How to make the Value of txtbox.Focus to True...........