Exception when ordering a grouped result set

I am using Lightspeed v4.0.1476.20948 (nightly 6 sept 2012) on the Nortwind database. I try to show the shippers with the most freight:

dataGridView1.DataSource = uow.Orders.GroupBy(o => o.ShipVia)
                    .Select(g => new { g.Key.CompanyName, TotalFreight = g.Sum(o => o.Freight) })
                    .OrderByDescending(r => r.TotalFreight)
                    .ToList();

I get the following exception:

System.NullReferenceException was unhandled
  Message=Object reference not set to an instance of an object.
  Source=Mindscape.LightSpeed.Linq
  StackTrace:
       at Mindscape.LightSpeed.Linq.Sqo.Aggregate.ApplyCriteria(LinqQueryPlanExpression plan, QueryExpression applyTo, Expression[] arguments)
       at Mindscape.LightSpeed.Linq.Sqo.ScalarCriteriaSqo.GetCriteria(LinqQueryPlanExpression plan, IEnumerable`1 arguments)
       at Mindscape.LightSpeed.Linq.Sqo.CriteriaSqo.ExtractMethodCriteria(LinqQueryPlanExpression plan, MethodCallExpression expression)
       at Mindscape.LightSpeed.Linq.Sqo.CriteriaSqo.ExtractCriteriaCore(LinqQueryPlanExpression plan, Expression expression)
       at Mindscape.LightSpeed.Linq.Sqo.CriteriaSqo.ExtractCriteria(LinqQueryPlanExpression plan, Expression expression)
       at Mindscape.LightSpeed.Linq.Sqo.CriteriaSqo.ExtractMemberCriteria(LinqQueryPlanExpression plan, MemberExpression member)
       at Mindscape.LightSpeed.Linq.Sqo.CriteriaSqo.ExtractCriteriaCore(LinqQueryPlanExpression plan, Expression expression)
       at Mindscape.LightSpeed.Linq.Sqo.CriteriaSqo.ExtractCriteria(LinqQueryPlanExpression plan, Expression expression)
       at Mindscape.LightSpeed.Linq.Sqo.CriteriaSqo.ExtractCriteriaCore(LinqQueryPlanExpression plan, Expression expression)
       at Mindscape.LightSpeed.Linq.Sqo.CriteriaSqo.ExtractCriteria(LinqQueryPlanExpression plan, Expression expression)
       at Mindscape.LightSpeed.Linq.Sqo.CriteriaSqo.ExtractCriteriaCore(LinqQueryPlanExpression plan, Expression expression)
       at Mindscape.LightSpeed.Linq.Sqo.CriteriaSqo.ExtractCriteria(LinqQueryPlanExpression plan, Expression expression)
       at Mindscape.LightSpeed.Linq.Sqo.OrderSqo.Evaluate(ExpressionVisitor visitor, MethodCallExpression expression)
       at Mindscape.LightSpeed.Linq.Plan.LinqQueryBuilder.VisitMethodCall(MethodCallExpression exp)
       at Mindscape.LightSpeed.Linq.Plan.LinqQueryBuilder.Visit(Expression exp)
       at Mindscape.LightSpeed.Linq.Plan.LinqQueryBuilder.Build(Expression translation, LinqQueryProvider provider)
       at Mindscape.LightSpeed.Linq.LinqQueryProvider.GetExecutionPlan(Expression expression)
       at Mindscape.LightSpeed.Linq.LinqQueryProvider.Execute(Expression expression)
       at Mindscape.LightSpeed.Linq.LinqQueryProvider.System.Linq.IQueryProvider.Execute(Expression expression)
       at Mindscape.LightSpeed.Linq.LinqQuery`1.GetEnumerator()
       at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
       at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
       at Northwind.Form1.button1_Click(Object sender, EventArgs e) in D:\Projects\Northwind\Northwind\Form1.cs:line 28
       at System.Windows.Forms.Control.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
       at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.ButtonBase.WndProc(Message& m)
       at System.Windows.Forms.Button.WndProc(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.Run(Form mainForm)
       at Northwind.Program.Main() in D:\Projects\Northwind\Northwind\Program.cs:line 18
       at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException: 

Thanks for reporting this - I have added in a fix and this will be available in tonights nightly build for you.

Thanks!
Jeremy

This is not actually fixed so that it works. Instead, it throws a new exception:

System.NotSupportedException: This type of ordering is not supported by LightSpeed, check that your ordering does not contain a value or aggregate function

Ordering by the value of an aggegrate function works in SQL, so I think it should work in Lightspeed.

Bugger sorry about that, you are indeed correct - a mix-up when posting the reply. Unfortunately this isn't something we can currently support, so I have tidied up the exception message here to more clearly indicate this. I have made a note of this so we can come back to try and have another look at this in the future but for now the use of constant values or aggregates are not valid in order by clauses either within LINQ or our native querying API.

Again, apologies for the mix-up on the original reply.

Jeremy