The Most Efficient ASP.NET Cache Clearing Method

asp.net c# cache-control caching entity-framework

Question

I am building an ASP.NET/Umbraco powered website which is very custom data driven via entity framework, we are having to cache quite a lot of the data queries (For example searches by keyword) as it's a busy site.

But when a user creates a new data entry, I need to clear all the cached queries (Searches etc..) so the new entry is available in the results.

So in my create, delete and update methods I am calling the following method:

public static void ClearCacheItems()
{
    var enumerator = HttpContext.Current.Cache.GetEnumerator();

    while (enumerator.MoveNext())
    {
        HttpContext.Current.Cache.Remove(enumerator.Key.ToString());
    }
}

Is this really bad? I can't see how else I am supposed to clear the cached items?

1
19
6/2/2011 9:27:24 AM

Popular Answer

The method you use is actually the correct way to clear your cache, there is just one minor 'error' in your code. The enumerator only is valid as long as the original collection remains unchanged. So while the code might work most of the time, there might be small errors in certain situations. Best is to use the following code, which does essentially the same, but does not use the enumerator directly.

List<string> keys = new List<string>();
IDictionaryEnumerator enumerator = Cache.GetEnumerator();

while (enumerator.MoveNext())
  keys.Add(enumerator.Key.ToString());

for (int i = 0; i < keys.Count; i++)
  Cache.Remove(keys[i]);
11
6/2/2011 9:35:05 AM


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