ASP.NET Global中Context.Cache.Insert（）

Question

public void Back(String k, Object v, CacheItemRemovedReason r)
      {
         try
         {
           Cache cache =new Cache();
          cache.Insert("linli1","123",null,System.DateTime.Now.AddMinutes(0.1),Cache.NoSlidingExpiration,System.Web.Caching.CacheItemPriority.Default,new System.Web.Caching.CacheItemRemovedCallback(Back));
     
         }
         catch
         {
            
         }      }

protected void Application_Start(Object sender, EventArgs e)
{
 Context.Cache.Insert("linli","123",null,System.DateTime.Now.AddMinutes(0.1),Cache.NoSlidingExpiration,System.Web.Caching.CacheItemPriority.Default,new System.Web.Caching.CacheItemRemovedCallback(Back));
}
在回调时的Back 函数异常，为什么，怎么解决？

Answer 1

Catch到的提示的异常信息是什么?

Answer 2

{"Object reference not set to an instance of an object." 
帮忙的好兄弟可以复制到Global文件中

Answer 3

public void Back(String k, Object v, CacheItemRemovedReason r)
      {
         try
         {
//           Cache cache =new Cache();
          httpContext.cache.Insert("linli1","123",null,System.DateTime.Now.AddMinutes(0.1),Cache.NoSlidingExpiration,System.Web.Caching.CacheItemPriority.Default,new System.Web.Caching.CacheItemRemovedCallback(Back));
     
         }
         catch
         {
            
         }      }