title: ASP.net Cache Absolute Expiration not working
body: <p>I am storing a single integer value in HttpContext.Cache with an absolute expiration time of 5 minutes from now. However, after waiting 6 minutes (or longer), the integer value is still in the Cache (i.e. it's never removed even though the absolute expiration has passed). Here is the code I am using:</p>
  
  <pre><code>public void UpdateCountFor(string remoteIp)
  {
      // only returns true the first time its run
      // after that the value is still in the Cache
      // even after the absolute expiration has passed
      // so after that this keeps returning false
      if (HttpContext.Current.Cache[remoteIp] == null)
      {
          // nothing for this ip in the cache so add the ip as a key with a value of 1
          var expireDate = DateTime.Now.AddMinutes(5);
          // I also tried:
          // var expireDate = DateTime.UtcNow.AddMinutes(5); 
          // and that did not work either.
          HttpContext.Current.Cache.Insert(remoteIp, 1, null, expireDate, Cache.NoSlidingExpiration, CacheItemPriority.Default, null);
      }
      else
      {
          // increment the existing value
          HttpContext.Current.Cache[remoteIp] = ((int)HttpContext.Current.Cache[remoteIp]) + 1;
      }
  }
  </code></pre>
  
  <p>The first time I run UpdateCountFor("127.0.0.1") it inserts 1 into the cache with key "127.0.0.1" and an absolute expiration of 5 minutes from now as expected. Every subsequent run then increments the value in the cache. However, after waiting 10 minutes it continues to increment the value in the Cache. The value never expires and never gets removed from the Cache. Why is that?</p>
  
  <p>It's my understanding that an absolute expiration time means the item will get removed approximately at that time. Am I doing something wrong? Am I misunderstanding something?</p>
  
  <p>I'm expecting the value to be removed from the Cache after 5 minutes time, however it stays in there until I rebuild the project.</p>
  
  <p>This is all running on .NET 4.0 on my local machine.</p>