List<string> keys = new List<string>();
// retrieve application Cache enumerator
IDictionaryEnumerator enumerator = HttpRuntime.Cache.GetEnumerator();
// copy all keys that currently exist in Cache
while (enumerator.MoveNext())
{
keys.Add(enumerator.Key.ToString());
}
// delete every key from cache
for (int i = 0; i < keys.Count; i++)
{
HttpRuntime.Cache.Remove(keys[i]);
}