Data can be stored on the client – using the view state of the page, or on the server in a variable session state or application, or using the server cache.
ASP.NET implements System.Web.Caching.Cache class to store objects that require a large amount of server resources to be created, so that they do not have to be recreated each time it is needed.
You can access via code information about a class instance cache through the property cache, the object of the HttpContext or Page object.
Expiration policy for items in cache:
- Specific time: absolute expiration
- May also expire if not accessed for a period of time: sliding expiration
Insert Into cache
Cache.Insert("myDataSet", ds, Nothing, DateTime.Now.AddSeconds(30), System.TimeSpan.Zero)
Using Cache:
If Cache("myDataSet") Is Nothing Then MyDataSet() 'DataSet from database Else ds = CType(Cache("myDataSet"), DataSet) ' DataSet from cache. End If
Clear Cache:
Cache.Remove("myDataSet")
Clear ALL Cache vars:
Dim enumerator As IDictionaryEnumerator = HttpContext.Current.Cache.GetEnumerator()
While enumerator.MoveNext()
HttpContext.Current.Cache.Remove(enumerator.Key)
End While
Note that, this technique is not efficient for pages with OutputCache type. for clearing this type cached memory, you should use below code line.
HttpRuntime.Close()
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