NullReference Exception was unhandled

System.NullReferenceException was unhandled
  Message="Odwołanie do obiektu nie zostało ustawione na wystąpienie obiektu."
  Source="Mindscape.LightSpeed.Linq"
  StackTrace:
       w Mindscape.LightSpeed.Linq.Plan.LinqQueryPlanExpression.ExtractRangeVariablesFromNewExpression(Expression expr)
       w Mindscape.LightSpeed.Linq.Plan.LinqQueryPlanExpression.ExtractRangeVariables(Expression expression)
       w Mindscape.LightSpeed.Linq.Plan.LinqQueryPlanExpression.ExtractRangeVariables(Expression expression)
       w Mindscape.LightSpeed.Linq.Sqo.Select.Evaluate(ExpressionVisitor visitor, MethodCallExpression expression)
       w Mindscape.LightSpeed.Linq.Plan.LinqQueryBuilder.VisitMethodCall(MethodCallExpression exp)
       w Mindscape.LightSpeed.Linq.Plan.LinqQueryBuilder.Visit(Expression exp)
       w Mindscape.LightSpeed.Linq.Plan.LinqQueryBuilder.Build(Expression translation, LinqQueryProvider provider)
       w Mindscape.LightSpeed.Linq.LinqQueryProvider.GetExecutionPlan(Expression expression)
       w Mindscape.LightSpeed.Linq.LinqQueryProvider.Execute(Expression expression)
       w Mindscape.LightSpeed.Linq.LinqQueryProvider.System.Linq.IQueryProvider.Execute(Expression expression)
       w Mindscape.LightSpeed.Linq.LinqQuery`1.GetEnumerator()
       w System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
       w System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
       w Manager.Events.EventViewModel.LoadAllEvents() w F:\Checkout\areva.spdc\Manager\Manager\EventViewModel.cs:wiersz 27
       w Manager.PageEvents.m_btn_events_open_Click(Object sender, RoutedEventArgs e) w F:\Checkout\areva.spdc\Manager\Manager\PageEvents.xaml.cs:wiersz 47
       w System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
       w System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
       w System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
       w System.Windows.UIElement.RaiseEvent(RoutedEventArgs e)
       w System.Windows.Controls.Primitives.ButtonBase.OnClick()
       w System.Windows.Controls.Button.OnClick()
       w System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(MouseButtonEventArgs e)
       w System.Windows.UIElement.OnMouseLeftButtonUpThunk(Object sender, MouseButtonEventArgs e)
       w System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
       w System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
       w System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
       w System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
       w System.Windows.UIElement.ReRaiseEventAs(DependencyObject sender, RoutedEventArgs args, RoutedEvent newEvent)
       w System.Windows.UIElement.CrackMouseButtonEventAndReRaiseEvent(DependencyObject sender, MouseButtonEventArgs e)
       w System.Windows.UIElement.OnMouseUpThunk(Object sender, MouseButtonEventArgs e)
       w System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
       w System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
       w System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
       w System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
       w System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
       w System.Windows.UIElement.RaiseEvent(RoutedEventArgs args, Boolean trusted)
       w System.Windows.Input.InputManager.ProcessStagingArea()
       w System.Windows.Input.InputManager.ProcessInput(InputEventArgs input)
       w System.Windows.Input.InputProviderSite.ReportInput(InputReport inputReport)
       w System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel)
       w System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
       w System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
       w MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
       w MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
       w System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Boolean isSingleParameter)
       w System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler)
       w System.Windows.Threading.Dispatcher.WrappedInvoke(Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler)
       w System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Boolean isSingleParameter)
       w System.Windows.Threading.Dispatcher.Invoke(DispatcherPriority priority, Delegate method, Object arg)
       w MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
       w MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
       w System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame)
       w System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame)
       w System.Windows.Threading.Dispatcher.Run()
       w System.Windows.Application.RunDispatcher(Object ignore)
       w System.Windows.Application.RunInternal(Window window)
       w System.Windows.Application.Run(Window window)
       w System.Windows.Application.Run()
       w Manager.App.Main() w F:\Checkout\areva.spdc\Manager\Manager\obj\Release\App.g.cs:wiersz 0
       w System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
       w System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       w Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       w System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       w System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       w System.Threading.ThreadHelper.ThreadStart()
  InnerException:

This is how I created the context and the unit of work :

LightSpeedContext<EventsLogModelUnitOfWork> m_ctx = new LightSpeedContext<EventsLogModelUnitOfWork>()
            {
                ConnectionString = String.Format("data source={0}", dbname),
                DataProvider = DataProvider.SQLite3
            };
EventsLogModelUnitOfWork m_unit = m_ctx.CreateUnitOfWork();

And the below code generated the exception

if (Events != null && m_database != null)
            {
                Events.Clear();
                Events = m_unit.EventsLogs
                    .Select(ev => new EventModel(ev))
                    .ToList();
            }

What did I mess up?

The NullReferenceException is a bug, but your query would probably have failed anyway because of the projection in the Select.  ev => new EventModel(ev) looks to LINQ like a projection, like selecting a named or anonymous type (e.g. ev => new { ev.Id, ev.Name }), which means we're looking for a property to use in the projection (e.g. Id or Name).  In your case, there is no such property, and we therefore cannot translate this into a projection query.

Depending on EventModel's requirements, you need to either:

* Add a new constructor to EventModel, which takes individual properties, e.g. public EventModel(int id, string name); or

* Initialise the properties of EventModel from properties of the EventsLogs, e.g. ev => new EventModel { Id = ev.Id, Name = ev.Name }; or

* Run the Select client-side, by putting it after the ToList() call: m_unit.EventsLogs.ToList().Select(ev => new EventModel(ev)).

The first two will result in projection SELECT queries which only load the required columns; the last will fully materialise the EventsLogs entities in the unit of work.  Thus, if the EventModel objects are meant to be disconnected from the EventsLogs objects (just using them for initialisation data) then the first two options are more appropriate (but you may choose to use the third model anyway for convenience if the EMs are loading zillions of properties from the ELs); if the EventModel objects retain and wrap their EventsLogs entities, then the third option is more appropriate.

Also we have added a small fix for this issue which will be included in the next nightly build (20100327) which will resolve the NullReferenceException which is being thrown in this situation. The query would succeed, but as Ivan rightly points out this would run as a client side projection so the full entity will need to be loaded to pass it through to the constructor of EventModel. If you are able to select out the specific properties of an EventLog to initialize the EventModel then this would lead to a much more efficient query.