c# 如何用lock解决缓存击穿

private static object GetMemoryCacheLockObject(string key)
    {
      string cacheLockKey = string.Format(MemoryCacheLockObjectFormat, key);
      lock (CacheObject)
      {
        var lockObject = CacheObject[cacheLockKey];
        if (lockObject == null)
        {
          // 取得每個 Key專屬的 lock object；若同時有多個 thread要求相同資料，只會(到資料庫)查第一次，剩下的從 cache讀取
          lockObject = new object();
          CacheObject.Set(
            cacheLockKey,
            lockObject,
            new System.Runtime.Caching.CacheItemPolicy()
            {
              AbsoluteExpiration = DateTimeOffset.UtcNow.AddMinutes(10)
            }
          );
        }

        return lockObject;
      }
    }

public T Get<T>(string key, Func<T> getDataWork, TimeSpan absoluteExpireTime, bool forceRefresh = false, bool returnCopy = true) where T : class
    {
      try
      {
        lock (GetMemoryCacheLockObject(key))
        {
          /*
System.ArgumentNullException: Value cannot be null.
at System.Threading.Monitor.Enter(Object obj)
at BQoolCommon.Helpers.Cache.MemoryCacheLayer.Get[T](String key, Func`1 getDataWork, TimeSpan absoluteExpireTime, Boolean forceRefresh, Boolean returnCopy) in D:\Source\BQoolCommon\BQoolCommon.Helpers\Cache\MemoryCacheLayer.cs:line 46
           */
          T result = CacheObject[key] as T;

          if (result != null && forceRefresh)
          {// 是否清除Cache，強制重查
            result = null;
          }

          if (result == null)
          {
            //執行取得資料的委派作業
            result = getDataWork();

            if (result != null)
            {
              Set(key, result, absoluteExpireTime);
            }
          }

          if (returnCopy)
          {
            //複製一份新的參考
            string serialize = JsonConvert.SerializeObject(result);
            return JsonConvert.DeserializeObject<T>(serialize);
          }
          else
          {
            return result;
          }
        }
      }
      catch
      {
        return getDataWork();
      }
    }

 T result = CacheObject[key] as T;

try
      {
        lock (GetMemoryCacheLockObject(key))
        {
          /*
System.ArgumentNullException: Value cannot be null.
at System.Threading.Monitor.Enter(Object obj)
at BQoolCommon.Helpers.Cache.MemoryCacheLayer.Get[T](String key, Func`1 getDataWork, TimeSpan absoluteExpireTime, Boolean forceRefresh, Boolean returnCopy) in D:\Source\BQoolCommon\BQoolCommon.Helpers\Cache\MemoryCacheLayer.cs:line 46
           */
          T result = CacheObject[key] as T;

string cacheLockKey = string.Format(MemoryCacheLockObjectFormat, key);
      lock (CacheObject)
      {
        var lockObject = CacheObject[cacheLockKey];
        if (lockObject == null)
        {
          // 取得每個 Key專屬的 lock object；若同時有多個 thread要求相同資料，只會(到資料庫)查第一次，剩下的從 cache讀取
          lockObject = new object();