Unity3D C# Enemy Find nearest Player Script

In this script which you attach to the Enemy Objects, you may find the nearest object Tagged "Player". The Enemy faces the Player, and chases within a proximity, with a given frequency. See below:

/// <summary>
/// AI character controller.
/// Just A basic AI Character controller
/// will looking for a Target and moving to and Attacking
/// </summary>

using UnityEngine;
using System.Collections;

[RequireComponent(typeof(CharacterSystem))]

public class AICharacterController : MonoBehaviour {

    public GameObject ObjectTarget;
    public string TargetTag = "Player";
    private CharacterSystem character;
    private int aiTime = 0;
    private float scanFrequency = 1.0f;
    private int aiState = 0;

    void Start () {
        character = gameObject.GetComponent<CharacterSystem>();
        InvokeRepeating ("ScanForTarget",0,scanFrequency);
    }
   
    void ScanForTarget() {
        ObjectTarget = GetNearestTaggedObject();
    }

    public GameObject GetNearestTaggedObject () {
        var nearestDistanceSqr = Mathf.Infinity;
        GameObject nearestObj = null;

        foreach (var obj in GameObject.FindGameObjectsWithTag(TargetTag)) {

            var objectPos = obj.transform.position;
            var distanceSqr = (objectPos - transform.position).sqrMagnitude;
           
            if (distanceSqr < nearestDistanceSqr) {
                nearestObj = obj;
                nearestDistanceSqr = distanceSqr;
            }
        }
        return nearestObj;
    }

    public float DistanceSquaredTo(GameObject source, GameObject target) {
        return Vector3.SqrMagnitude(source.transform.position - target.transform.position);
    }

    void Update () {
            //if (GameObject.Find("CharacterDakota").GetComponent<CharacterStatus>().HP > 0) {
           
        if (GameObject.Find("GameManager").GetComponent<GameManager>().Playing) {

            var direction = Vector3.zero;
            if(aiTime<=0){
                aiState = Random.Range(0,4);
                aiTime = Random.Range(10,100);
            }else{
                aiTime--;
            }
            if(ObjectTarget){
                //ObjectTarget = GameObject.FindGameObjectWithTag(TargetTag);   
                float distance = Vector3.Distance(ObjectTarget.transform.position,this.gameObject.transform.position);
               
                if(distance<=2){
                    transform.LookAt(ObjectTarget.transform.position);
                    if(aiTime<=0){
                        if(aiState == 1){
                            character.Attack();
                        }
                    }
                }else{
                    if(aiState == 1){
                        transform.LookAt(ObjectTarget.transform.position);
                        direction = this.transform.forward;
                        direction.Normalize();
                        character.Move(direction);
                    }
                }
               
            }else{
                ScanForTarget();
            }
        }
    }
}