Animation Script on GetKeyPressed

I have been working on a 2d game for about two weeks now. I am stuck on my animation script where if you press a key you would move forward and have the move forward animation play. This game I am working on is an RPG like game, so there is no jump but rather X and Y movement.

Here is my script so far:`
Animator anim;

 // Use this for initialization
 void Start () {
     anim = GetComponent<Animator>();
 }
 
 // Update is called once per frame
 void Update () {
 
 }


 public void WalkN(){
     if(Input.GetKeyDown(KeyCode.W)){
     anim.SetBool ("WalkN", true);
 }

     if(Input.GetKeyDown(KeyCode.S)){
         anim.SetBool ("WalkS", true);
 }
 
     if(Input.GetKeyDown(KeyCode.D)){
         anim.SetBool ("WalkE", true);
 }

     if(Input.GetKeyDown(KeyCode.A)){
         anim.SetBool ("WalkW", true);
 }

     if(Input.GetKeyUp(KeyCode.W)){
         anim.SetBool ("WalkN", false);
     }

     if(Input.GetKeyUp(KeyCode.A)){
         anim.SetBool ("WalkW", false);
     }

     if(Input.GetKeyUp(KeyCode.S)){
         anim.SetBool ("WalkS", false);
     }

     if(Input.GetKeyUp(KeyCode.D)){
         anim.SetBool ("WalkE", false);
     }

}`