Linq :Object reference not set to an instance of an object.

[john]

Dim dbNutBackupModel As New NutBackupModel

            Dim Query = From listcust In ( _
(From listcust0 In dbNutBackupModel.Customers.AsEnumerable _
Group Join listbackup1 In dbNutBackupModel.Backups On New With {listcust0.CustomerID} Equals New With {listbackup1.CustomerID} Into listbackup1_join = Group _
From listbackup1 In listbackup1_join.DefaultIfEmpty() _
Where _
  (Not listbackup1.CustomerID = Nothing) _
Group New With {listcust0, listbackup1} By _
  listcust0.CustomerName, _
  listbackup1.CustomerID _
 Into glist = Group _
Select _
  CustomerName, _
  CustomerID = CType(CustomerID, Int32?), _
  Maxdate = CType(glist.Max(Function(p) p.listbackup1.EndTime), DateTime?)) _
) _
Group Join listbackup In ( _
((From backups In dbNutBackupModel.Backups _
Select _
  backups.CustomerID, _
  backups.Success, _
  backups.EndTime) _
.Distinct())) On New With {.Maxdate = listcust.Maxdate} Equals New With {.Maxdate = listbackup.EndTime} Into listbackup_join = Group _
From listbackup In listbackup_join.DefaultIfEmpty() _
Select _
 listcust.CustomerName, _
 listcust.CustomerID, _
 Maxdate = CType(listcust.Maxdate, DateTime?), _
 Success = CType(listbackup.Success, Boolean?)
            ' Dim ItemsSource As New ListViewItem
            'ItemsSource = Query
            rgdDashBoard.DataSource = Query

Here ,
I got this exception


Anonymously Hosted DynamicMethods Assembly


   at lambda_method(ExecutionScope , VB$AnonymousType_2`3 )
   at System.Linq.Enumerable.WhereEnumerableIterator`1.MoveNext()
   at System.Linq.Lookup`2.Create[TSource](IEnumerable`1 source, Func`2 keySelector, Func`2 elementSelector, IEqualityComparer`1 comparer)
   at System.Linq.GroupedEnumerable`4.GetEnumerator()
   at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
   at System.Linq.Enumerable.<GroupJoinIterator>d__6a`4.MoveNext()
   at System.Linq.Enumerable.<SelectManyIterator>d__31`3.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at NutBackupWeb.Dashboard.rgdDashBoard_NeedDataSource(Object source, GridNeedDataSourceEventArgs e) in E:\Projects\NutStor\liya\NutBackup\NutBackup\Web\Dashboard.aspx.vb:line 76

Please help me on this ..

Thanks and Regards


Mukesh

[Thomas]

Hi John,

 this is a bit hard to follow, but you have got a null reference somewhere, possibly in the lambda of the Max.
I propose to break this statement down by using ToList() in between to isolate the issue.

Best wishes,
Thomas
the Telerik team