How to calculate the speed at which a rigidbody2d is actually moving ?

I am trying to figure out the speed of a rigidbody2D (it's velocity) (It's movement speed) so that I can animate a character. I need the character to stop the walking animation when it hits a wall (stops moving) The problem is that when my character walks into a wall, if the key is still held, I am still adding to the velocity. Therefore my code still thinks that it should try to play the walking animation.

Is there any code to determine the actual speed at which a rigid body is moving and not just being set to? Is there any better way of telling the animator to stop the animation when the player isn't moving?

I need a quickly updating solution. I have tried:

 if (GetComponent<Rigidbody2D>().isSleeping())

and

 if (gameObject.isStatic)

but they either don't work or are too slow at recognising that the player has stopped. Please help me solve this problem.

My current solution is:

 if (rb.velocity == 0) {
 anim.SetFloat ("Speed", 1);
 } else {
 anim.SetFloat ("Speed", 0);
 }