System.NullReferenceException: 未将对象引用设置到对象的实例

Question

“/”应用程序中的服务器错误。未将对象引用设置到对象的实例。说明: 执行当前 Web 请求期间，出现未处理的异常。请检查堆栈跟踪信息，以了解有关该错误以及代码中导致错误的出处的详细信息。 异常详细信息: System.NullReferenceException: 未将对象引用设置到对象的实例。源错误: 
行 37: 
行 38:                      //Get enumerator
行 39:                      IEnumerator<KeyValuePair<string, ADReport>>  CacheEnum = Items.GetEnumerator();
行 40:                      //Items.GetEnumerator();
行 41:                      //loop

Answer 1

Items.GetEnumerator();取出来是空的

Answer 2

很有可能是你的Items这个变量没有初始化实例，能提供你上下文更多源代码信息看看吗？

Answer 3

是什么问题，使得Items.GetEnumerator();取出来是空的呢？

Answer 4

   private int NCPM;
        private int NCPM_C;
    
         private void Page_Load(object sender, System.EventArgs e)
                 {
                     hlRefresh.NavigateUrl = Request.RawUrl;
                     //In a cluster, it might be nice to know which machine we are on.
                     litMachine.Text = System.Environment.MachineName;                     //Bind CachedItems
                     BindGrid();
                 }
    
   
                 //Bind the grid with items found in the cache.
                 private void BindGrid()
                 {
                     //Create an arraylist to hold our cacheditem details
                     ArrayList al = new ArrayList(); string KEY = "ADREPORT_LIST";
            IDictionary<string, ADReport> Items = (IDictionary<string, ADReport>)HttpContext.Current.
                Cache.Get(KEY);                     //Get enumerator
                     IEnumerator<KeyValuePair<string, ADReport>>  CacheEnum = Items.GetEnumerator();
                     //Items.GetEnumerator();
                     //loop
                     while (CacheEnum.MoveNext())
                     {
                         try
                         {
                             //Do we want to include this item
                             if(IncludeInList(CacheEnum.Current.Key.ToString()))
                             {
 IList il = CacheEnum.Current.Value as IList;
 ADReport dic = CacheEnum.Current.Value as ADReport;
 if(il != null || dic != null)
 {
al.Add(new CachedItem(CacheEnum.Current.Key.ToString(),CacheEnum.Current.Value.CPM, CacheEnum.Current.Value.CPM_C));
NCPM += CacheEnum.Current.Value.CPM;
NCPM_C += CacheEnum.Current.Value.CPM_C;
  }
                             }
                         }
                         catch{}
                     }
                     //set counter Literal
                     litCount.Text = NCPM.ToString();      litCount_C.Text = NCPM_C.ToString();
    
                     //Bind
                     //dgCachedItems.DataSource = al;
                     //dgCachedItems.DataBind();
    
                 }

Answer 5

你的HttpContext.Current.Cache.Get(KEY)
取出来是个null吧！？再往上查找一下原因？