animation works but wont stop

Hi,
I got my walking animation working but when i press w and release it it just keep looping and i just dont know what to do here is my script:

function Update()
{
if(Input.GetKeyDown("w"))
{
// Plays the walking animation - stops all other animations
animation.Play("WalkingAnime", PlayMode.StopAll);
}
}

and i have made it legacy etc but i just dont know what to do...