Why is my asp.net caching throwing an exception?

Question

I have a bunch of simple lookup tables cached in my asp.net application, since the source data is on a separate server from our main web architecture and does not change often. I read the answers and various documentation here, and I have a boot function that calls the following:

HttpContext.Current.Cache.Insert("CheckLocations", GetAllCheckLocations(), _
                                 Nothing, DateAdd(DateInterval.Day, 1, Now()), _
                                 System.Web.Caching.Cache.NoSlidingExpiration, _
                                 CacheItemPriority.Normal, _
                                 New CacheItemRemovedCallback(AddressOf CheckLocationsExpired))

For my expired cache callback, I have the following code.

Public Shared Sub CheckLocationsExpired(ByVal key As String, ByVal value As Object, ByVal reason As CacheItemRemovedReason)

   Dim dtCheckLocation As New ReferenceSchema.CheckLocationDataTable
   dtCheckLocation = GetAllCheckLocations()

   HttpContext.Current.Cache.Insert("CheckLocations", dtCheckLocation, Nothing, _
                                    DateAdd(DateInterval.Day, 1, Now()), _
                                    System.Web.Caching.Cache.NoSlidingExpiration, _
                                    CacheItemPriority.Normal, _
                                    New CacheItemRemovedCallback(AddressOf CheckLocationsExpired))

End Sub

For the record, the GetAllCheckLocations method simply calls the web service and parses the results in the stored data table.

Now, when I recompile the application for local testing, everything still works fine, but in my log file I found the following exception message:

System.NullReferenceException: ​​ . EAF.CacheMethods.CheckLocationsExpired( , , CacheItemRemovedReason) C:\Projects\HR\EAF 2.0\DAL\CacheMethods.vb: 434 System.Web.Caching.CacheEntry.CallCacheItemRemovedCallback(CacheItemRemovedCallback , CacheItemRemovedReason)

, , .

- , ? "", Reponse.Redirect, ?

Answer 1

, ? , .

Answer 2

HttpRuntime.Cache. , HttpContext.Current null, unit test .

Answer 3

My initial thought is that GetAllCheckLocations throws an exception or returns null.

Answer 4

Perhaps you are calling a method with AJAXProor something like that.