Why is my code not working? [please help]

I am trying to write numbers with a keypad and using a while loop to get the input from the user, every time I attempt to test it the game freezes . using UnityEngine; using System.Collections; using UnityEngine.UI;

 public class TCLockNum : MonoBehaviour {
 
     public Text Num;
     private enum States {lock_1, lock_2};
     private States myState;
     public string num;
     
     void Start () {
         state_lock_1();
         
     }
     void Update () {
         if (myState == States.lock_2) {
             state_lock_2();
         }
     }
     
     void state_lock_1 () {
         while (num.Length<6) {
             if (Input.GetKeyDown(KeyCode.Keypad1)) {
                 num=num+"1";
             }else if (Input.GetKeyDown(KeyCode.Keypad2)) {
                 num=num+"2";    
             }else if (Input.GetKeyDown(KeyCode.Keypad3)) {
                 num=num+"3";
             }else if (Input.GetKeyDown(KeyCode.Keypad4)) {
                 num=num+"4";
             }else if (Input.GetKeyDown(KeyCode.Keypad5)) {
                 num=num+"5";
             }else if (Input.GetKeyDown(KeyCode.Keypad6)) {
                 num=num+"6";
             }else if (Input.GetKeyDown(KeyCode.Keypad7)) {
                 num=num+"7";
             }else if (Input.GetKeyDown(KeyCode.Keypad8)) {
                 num=num+"8";    
             }else if (Input.GetKeyDown(KeyCode.Keypad9)) {
                 num=num+"9";
             }else if (Input.GetKeyDown(KeyCode.Keypad0)) {
                 num=num+"0";
             }
         }
         Num.text=num;
     }
     
     void state_lock_2 () {
     
     }
 }