Question

I am currently building a web site and I just implemented SqlCacheDependency using LinqToSQL like so.

   public IQueryable<VictoryList> GetVictoryList()    {                 string cacheKey = HttpContext.Current.User.Identity.Name + 'victoryCacheKey';                 IQueryable<VictoryList> cachednews = (IQueryable<VictoryList>)HttpContext.Current.Cache.Get(cacheKey);                  if (cachednews == null)                 {                      var results = from v in _datacontext.ViewVictoryLists                                   orderby _datacontext.GetNewId()                                   select new VictoryList                                   {                                       MemberID = v.MemberID,                                       Username = v.Aspnetusername,                                       Location = v.Location,                                       DaimokuGoal = v.DaimokuGoal,                                       PreviewImageID = v.PreviewImageID,                                       TotalDaimoku = v.TotalDaimoku,                                       TotalDeterminations = v.TotalDeterminations,                                       DeterminationID = v.DeterminationID,                                       DeterminationName = v.DeterminationName                                   };                     SqlCacheDependency dependency =                      new SqlCacheDependency(_datacontext.GetCommand(results) as SqlCommand);                      HttpContext.Current.Cache.Add(cacheKey, results, dependency, DateTime.MaxValue,                                   TimeSpan.Zero, CacheItemPriority.Normal, null);                       return results.ToList().AsQueryable();                 }                 return cachednews;    } 

It appears to be working as things are noticbly faster especially on some complex queries, however while looking at things in SQLProfiler I still see the query run through, I’m using the CommandBroker mode of SqlCacheDependency. Should I still see the query even though the data is obviously coming from a cached object?

Answer 1

I think that the problem is that you are storing IQueryable’s in your cache, and then cachednews contains an IQueryable that hits the database.

Try the following changes.

public IQueryable<VictoryList> GetVictoryList() {             // ...             if (cachednews == null)             {                  var results = from // ...                 results = results.ToList().AsQueryable(); // force query execution                  SqlCacheDependency dependency = // ...;                 HttpContext.Current.Cache.Add(cacheKey,                      results, // now just the result are stored                     dependency,                      DateTime.MaxValue,                     TimeSpan.Zero,                      CacheItemPriority.Normal,                      null);                   return results;             }             return cachednews; }