在Cache.Add之后直接触发SqlCacheDependency移除回调函数

我有一个问题与SqlCacheDependency，我不能绕我的头。当使用通知查询时，一旦我向缓存添加一些东西，CacheItemRemovedCallback就会触发(当我使用databaseEntryName和tableName时，它会起作用，但这对我来说是钝的)。我已经检查了http://msdn.microsoft.com/en-us/library/ms181122.aspx大约20次，但我仍然找不到我做错了什么。

我使用的代码:

string connString = MsSqlUtil.GetConnectionString();
System.Web.Caching.SqlCacheDependencyAdmin.EnableNotifications(connString);
System.Web.Caching.SqlCacheDependencyAdmin.EnableTableForNotifications(connString, "Product");
SqlDependency.Start(connString);
Product product = ProductProvider.Get(10);
using (SqlConnection connection = new SqlConnection(connString))
{
  SqlCommand cmdProduct = new SqlCommand(@"
  SET ANSI_NULLS ON
  SET ANSI_PADDING ON
  SET ANSI_WARNINGS ON
  SET CONCAT_NULL_YIELDS_NULL ON
  SET QUOTED_IDENTIFIER ON
  SET NUMERIC_ROUNDABORT OFF
  SET ARITHABORT ON
  SET TRANSACTION ISOLATION LEVEL READ COMMITTED 
  SELECT dbo.Product.ProductId, dbo.Product.Name FROM dbo.Product WHERE dbo.Product.ProductId = 10", connection);
  SqlCacheDependency myProductDependency = new SqlCacheDependency(cmdProduct);
  if (connection.State == ConnectionState.Closed)
  {
    connection.Open();
  }
  using (SqlDataReader reader = cmdProduct.ExecuteReader())
  {
    while (reader.Read())
    {
    }
  }
  HttpContext.Current.Cache.Add("Product:10", product, myProductDependency, Cache.NoAbsoluteExpiration, Cache.NoSlidingExpiration, CacheItemPriority.Normal, OnRemove);
}

//Callback
public static void OnRemove(string key, object cacheItem, System.Web.Caching.CacheItemRemovedReason reason)
{
//this fires directly and the reason is always DependencyChanged however nothing has changed in the database, weird!
}

我明白查询一定有问题，因为http://msdn.microsoft.com/en-us/library/ms181122.aspx告诉我"如果这些选项或隔离级别没有适当设置，则在执行SELECT语句后立即触发通知"，但是我不知道是什么错了。ProductId列的类型为int，名称为nvarchar(50)