无法挂接事件

我正在尝试将 BasicLaser 类的事件安装在 BlueShip 类中，所以基本上这个事件将每 n 个时间单位触发一次。
这是与精灵"连接"的蓝船类

using UnityEngine;
using System.Collections.Generic;
using System.Timers;
using System;
    public class BlueShip : MonoBehaviour
    {
        enum LaserTypes { BASIC_LASER };
        private float speed_ = 100f;
        private List<GameObject> laser_ = new List<GameObject>();
        private GameObject currentLaser_;
        private Transform transform_;
        private Vector3 currentPosition_;
        private bool isElapsed_ = true;
        // Use this for initialization
        void Start()
        {
            transform_ = transform;
            /*Basic laser is the default and it's guaranteed to be installed at the beginning of the game*/
            laser_.Add((GameObject)Resources.Load("BasicLaser"));
            currentLaser_ = laser_[(int)LaserTypes.BASIC_LASER];
            laser_[0].GetComponent<BasicLaser>().timerElapsed += new TimerElapsed (BasicLaser_timerElapsed);    
//HERE I'M adding observer to this event but look for line named *2 in class BasicLaser

        }  
        public void BasicLaser_timerElapsed(object sender, EventArgs e)
        {/*this is supposed to react to event timerElapsed in BasicLaser*/
            isElapsed_ = true;
        }

        // Update is called once per frame
        void Update()
        {
            var amtToMove = Input.GetAxis("Horizontal") * speed_ * Time.deltaTime;
            transform_.Translate(Vector3.right * amtToMove);
            /*Those below set the position for laser to be instantiated at*/
            currentPosition_.x = transform_.position.x;
            currentPosition_.y = transform_.position.y + (this.transform.localScale.y / 2) + currentLaser_.transform.localScale.y;
            currentPosition_.z = transform_.position.z;

            if (Input.GetKeyDown(KeyCode.UpArrow))
            {
                if (isElapsed_)
                {
                    var t = Instantiate(laser_[(int)LaserTypes.BASIC_LASER], currentPosition_, Quaternion.identity);
                    isElapsed_ = false;
                }
            }
        }
    }

//BasicLaser class  which is "connected" to a BasicLaser prefab in unity
    using UnityEngine;
    using System.Collections;
    using System.Diagnostics;
    using System;
    public delegate void TimerElapsed(object sender,EventArgs e);
        public class BasicLaser : MonoBehaviour
        {
            private float speed_ = 500f;
            private static uint frequency_ = 2;//the frequency with which this laser can be fired
            private static Stopwatch stopWatch_ = new Stopwatch();
            public event TimerElapsed timerElapsed;//HERE IS THE EVENT
            public uint Frequency
            {
                get { return frequency_; }
                set { frequency_ = value; }
            }
            private Transform transform_;
            // Use this for initialization
            void Start()
            {
                transform_ = transform;
                stopWatch_.Start();
            }

            // Update is called once per frame
            void Update()
            {
                var amtToMove = speed_ * Time.deltaTime;
                transform_.Translate(Vector3.up * amtToMove);
            var t = stopWatch_.Elapsed.Milliseconds;
                if (t > frequency_)
                {
                    stopWatch_ = new Stopwatch();
                    stopWatch_.Start();
                    if (timerElapsed != null)//*2 THIS IS ALWAYS NULL!!!  
     even though I've hooked it in BlueShip class, what's going on?
                    {
                        timerElapsed(this, EventArgs.Empty);//raises the event
                    }
                }
                if (transform.position.y >= Screen.height)
                {
                    Destroy(gameObject);
                }
            }
        }