c# - Control is not getting focused on Keyup event -

hi have created dynamic combo box textbox , button appear dropdown style, every thing works fine handled keyup event textbox when user enter text search results , display them

 private void textbox1_keyup(object sender, keyeventargs e)  {      //some code filter data       textbox1.focus();  } 

but unable set focus textbox after results getting displayed can 1 me

code used here

http://www.planetsourcecode.com/vb/scripts/showcode.asp?txtcodeid=8554&lngwid=10

i have found focus() method bit flaky.

other options:

textbox1.select(textbox1.text.length - button1, 1); 

...or simply:

textbox1.select(); 

if can verify else going wrong, might off base, otherwise might fighting weirdness.