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

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  1. john
    john avatar
    4 posts
    Member since:
    Aug 2011

    Posted 30 Aug 2011 Link to this post

    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

  2. Thomas
    Thomas avatar
    590 posts

    Posted 31 Aug 2011 Link to this post

    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,
    the Telerik team

    Thank you for being the most amazing .NET community! Your unfailing support is what helps us charge forward! We'd appreciate your vote for Telerik in this year's SQL Server Community Awards. We are competing in TWO categories and every vote counts! VOTE for Telerik NOW >>

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