Another problem with MVC controls

I am using the Telerik MVC grid control again.  When I try to use sorting, I get an "Object reference not set to an instance of an object." error.

Full stack trace is at the bottom of the post.

I am using the latest 2.2 nightly build.

The error occurs in the extension method

        public static void Each<T>(this IEnumerable<T> instance, Action<T> action)
        {
            foreach (T item in instance)   /// << here
            {
                action(item);
            }
        }

Instance is

+        instance    {Mindscape.LightSpeed.Linq.LinqQuery<CmsModels.Entities.ToDoItem>}    System.Collections.Generic.IEnumerable<CmsModels.Entities.ToDoItem> {Mindscape.LightSpeed.Linq.LinqQuery<CmsModels.Entities.ToDoItem>}

I retrive my objects using

        private IEnumerable<ToDoItem> GetTodoItems(string filter)
        {
            IEnumerable<ToDoItem> items = from i in _AccRepository.GetUserToDo(CmsUser)
                                          where !i.CompletedDate.HasValue
                                          orderby i.DueDate
                                          select i;

            return items;
        }

Stack trace

Object reference not set to an instance of an object.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:


Line 52:         public static void Each<T>(this IEnumerable<T> instance, Action<T> action)
Line 53:         {
Line 54:             foreach (T item in instance)
Line 55:             {
Line 56:                 action(item);
 

Source File: D:\dev\dotnet\Components\Telerik_Extensions_for_ASPNET_MVC\Source\Telerik.Web.Mvc\Extensions\EnumerableExtensions.cs    Line: 54

Stack Trace:


[NullReferenceException: Object reference not set to an instance of an object.]
   Mindscape.LightSpeed.Linq.Sqo.OrderSqoBase.OnVisit(LinqQueryTranslator visitor, MethodCallExpression expression) +214
   Mindscape.LightSpeed.Linq.QueryMethodBase`1.PerformVisit(LinqQueryTranslator visitor, T expression) +39
   Mindscape.LightSpeed.Linq.LinqQueryTranslator.VisitMethodCall(MethodCallExpression m) +75
   Mindscape.LightSpeed.Linq.ExpressionVisitor.Visit(Expression exp) +566
   Mindscape.LightSpeed.Linq.Sqo.Take.OnVisit(LinqQueryTranslator visitor, MethodCallExpression expression) +80
   Mindscape.LightSpeed.Linq.QueryMethodBase`1.PerformVisit(LinqQueryTranslator visitor, T expression) +39
   Mindscape.LightSpeed.Linq.LinqQueryTranslator.VisitMethodCall(MethodCallExpression m) +75
   Mindscape.LightSpeed.Linq.ExpressionVisitor.Visit(Expression exp) +566
   Mindscape.LightSpeed.Linq.LinqQueryTranslator.Translate(Expression expression, IUnitOfWork unitOfWork, String viewName) +92
   Mindscape.LightSpeed.Linq.LinqQueryProvider.Execute(Expression expression) +107
   Mindscape.LightSpeed.Linq.LinqQueryProvider.System.Linq.IQueryProvider.Execute(Expression expression) +36
   Mindscape.LightSpeed.Linq.LinqQuery`1.System.Collections.Generic.IEnumerable<T>.GetEnumerator() +48
   Telerik.Web.Mvc.Extensions.EnumerableExtensions.Each(IEnumerable`1 instance, Action`1 action) in D:\dev\dotnet\Components\Telerik_Extensions_for_ASPNET_MVC\Source\Telerik.Web.Mvc\Extensions\EnumerableExtensions.cs:54
   Telerik.Web.Mvc.UI.Grid`1.WriteRows(IGridRenderer`1 renderer) in D:\dev\dotnet\Components\Telerik_Extensions_for_ASPNET_MVC\Source\Telerik.Web.Mvc\UI\Grid\Grid.cs:480
   Telerik.Web.Mvc.UI.Grid`1.WriteTable(IGridRenderer`1 renderer) in D:\dev\dotnet\Components\Telerik_Extensions_for_ASPNET_MVC\Source\Telerik.Web.Mvc\UI\Grid\Grid.cs:422
   Telerik.Web.Mvc.UI.Grid`1.WriteHtml(HtmlTextWriter writer) in D:\dev\dotnet\Components\Telerik_Extensions_for_ASPNET_MVC\Source\Telerik.Web.Mvc\UI\Grid\Grid.cs:380
   Telerik.Web.Mvc.UI.ViewComponentBase.Render() in D:\dev\dotnet\Components\Telerik_Extensions_for_ASPNET_MVC\Source\Telerik.Web.Mvc\UI\ViewComponentBase.cs:161
   Telerik.Web.Mvc.UI.ViewComponentBuilderBase`2.Render() in D:\dev\dotnet\Components\Telerik_Extensions_for_ASPNET_MVC\Source\Telerik.Web.Mvc\UI\ViewComponentBuilderBase.cs:137
   ASP.views_acc_todoitems_aspx.__RenderContent2(HtmlTextWriter __w, Control parameterContainer) in d:\dev\dotnet\Projects\CmsWeb\CmsWeb\Views\Acc\ToDoItems.aspx:31
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +256
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +19
   System.Web.UI.Control.Render(HtmlTextWriter writer) +10
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +99
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   ASP.views_shared_site_master.__Render__control1(HtmlTextWriter __w, Control parameterContainer) in d:\dev\dotnet\Projects\CmsWeb\CmsWeb\Views\Shared\Site.Master:60
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +256
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +19
   System.Web.UI.Control.Render(HtmlTextWriter writer) +10
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +99
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +134
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +19
   System.Web.UI.Page.Render(HtmlTextWriter writer) +29
   System.Web.Mvc.ViewPage.Render(HtmlTextWriter writer) +59
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +99
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1266

 

Having a bit of trouble reproducing this one I'm afraid.  I noticed there's a Take in your stack trace which isn't part of the original query in your code -- is that something that Telerik adds?  Or part of GetUserToDo?  I tried adding a Take to our test case but still couldn't get an exception.  Do you have access to the full query as it stands when Telerik enumerate it (i.e. after they've added their clauses)?  Thanks!

The Take is added by Telerik as part of the paging.

The sorting occurs as follows:

        public IQueryable Sort()
        {
            IQueryable query = queryable;
            bool isFirst = true;

            foreach (var descriptor in this.sortDescriptors)
            {
                Type memberType = typeof(object);
                var descriptorBuilder = ExpressionBuilderFactory.MemberAccess(queryable.ElementType, memberType, descriptor.Member);
                var expression = descriptorBuilder.CreateLambdaBLOCKED EXPRESSION;

                string methodName = "";
                if (isFirst)
                {
                    methodName = descriptor.SortDirection == ListSortDirection.Ascending ?
                        "OrderBy" : "OrderByDescending";
                    isFirst = false;
                }
                else
                {
                    methodName = descriptor.SortDirection == ListSortDirection.Ascending ?
                        "ThenBy" : "ThenByDescending";
                }

                query = query.Provider.CreateQuery(
                    Expression.Call(
                        typeof(Queryable),
                        methodName,
                        new[] { query.ElementType, expression.Body.Type },
                        query.Expression,
                        Expression.Quote(BLOCKED EXPRESSION);

            }
            return query;
        }

After this, query._expression is

{value(Mindscape.LightSpeed.Linq.LinqQuery`1[CmsModels.Entities.ToDoItem]).Select(e => e).Where(t => (t.UserId = Convert(value(CmsModels.Repositories.AccRepository+<>c__DisplayClass8).user.Id))).Where(i => Not(i.CompletedDate.HasValue)).OrderBy(i => i.DueDate).OrderBy(item => IIF((item != null), item.ClaimReference, null))}

I have tried removing my initial ordering, but that doesn't help.

Thanks for all the detailed info!  I noticed in the final expression this:

OrderBy(item => IIF((item != null), item.ClaimReference, null)

Any idea where this clause is coming from?  I also noticed this:

Where(t => (t.UserId = Convert(value(CmsModels.Repositories.AccRepository+<>c__DisplayClass8).user.Id)))

I'm not quite sure what's going on inside AccRepository here -- a closure or an iterator I guess (or possibly an anonymous type, though it doesn't look like one).  Can you shed any light on what might be providing this .user property?  Or maybe post the definition of AccRepository.GetUserToDo?

Finally, our horrible forum software has removed the details of CreateLambda... and Expression.Quote... in the Sort method you posted.  Could you perhaps copy the Sort() body into a text file and attach it via the Options tab.  Sorry to be annoying, this is a problem with the forum software which I need to make JD fix...

Thanks for your help in reproducing this!

The orderby is coming from the grid when I click on a header to order it.  Without the order by, the code works, with it, I get the error.

AccRepository

        public IQueryable<ToDoItem> GetUserToDo(User user)
        {
            IQueryable<ToDoItem> items = from t in UnitOfWorkScope.Current.ToDoItems
                                            where t.UserId == user.Id
                                            select t;
            return items;
        }

Any ideas?  This I get this problem on every grid.

Hi Sean,

Looks like the reason for the exception is the IFF (conditional) based OrderBy being added in to the query and this is unsupported in our LINQ provider.

Looking at it though, the inclusion of that seems a bit odd - if I am reading it correctly it should just be adding a OrderBy for the property rather than needing a conditional in there - is that the column you are sorting on? (there are 2 order bys in the example you specified above..)

Jeremy

That is the column I am sorting by.  I can remove my initial sort but I still get the same error.

Thanks Sean - Ill have a look at what the Telerik control is doing here to try and understand why it needs to build up its ordering query this way rather than just using a normal OrderBy(property). Will let you know what I find.

Thanks.  However don't get too exercised over it.  After another 1/2 day spent with the grid I am about ready to give up and go back to the MvcContrib grid.