Cannot access a disposed object. Databinding Telerik RadGrid using NeedDataSource event.

Hello!

Have you used maybe Telerik RadGrid control? When I try to use NeedDataSource event:

http://www.telerik.com/help/aspnet-ajax/grdadvanceddatabinding.html

I'm gettint this error:

System.ObjectDisposedException: Cannot access a disposed object. Object name: 'dbLightSpeedModelUnitOfWork'.

Generated: Tue, 10 Feb 2009 18:57:11 GMT

System.Web.HttpUnhandledException: Exception of type 'System.Web.HttpUnhandledException' was thrown. ---> System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'dbLightSpeedModelUnitOfWork'.
   at Mindscape.LightSpeed.UnitOfWorkBase.EnsureNotDisposed()
   at Mindscape.LightSpeed.UnitOfWorkBase.Find[TEntity](Query query)
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle._InvokeMethodFast(Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner)
   at System.RuntimeMethodHandle.InvokeMethodFast(Object target, Object[] arguments, Signature sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at Mindscape.LightSpeed.Linq.ProjectionStrategy.ExecuteEntityQuery(Query query, IUnitOfWork unitOfWork)
   at Mindscape.LightSpeed.Linq.ProjectionStrategy.Execute(Query query, IUnitOfWork unitOfWork)
   at Mindscape.LightSpeed.Linq.LinqQueryExecutionPlan.Execute()
   at Mindscape.LightSpeed.Linq.LinqQueryTranslator.Translate(Expression expression, IUnitOfWork unitOfWork, String viewName)
   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.System.Collections.IEnumerable.GetEnumerator()
   at Telerik.Web.UI.GridResolveEnumerable.GetCollectionItemType(Boolean noItemsInEnumerator, Type& itemType, Object& firstObject)
   at Telerik.Web.UI.GridResolveEnumerable.ParseProperties()
   at Telerik.Web.UI.GridResolveEnumerable.Initialize()
   at Telerik.Web.UI.GridResolveEnumerable.EnsureInitialized()
   at Telerik.Web.UI.GridEnumerableFromDataView..ctor(GridTableView owner, IEnumerable enumerable, Boolean CaseSensitive, Boolean autoGenerateColumns, GridColumnCollection presentColumns, String[] additionalField, Boolean retrieveAllFields)
   at Telerik.Web.UI.GridDataSourceHelper.CreateGridEnumerable(GridTableView owner, IEnumerable enumerable, Boolean caseSensitive, Boolean autoGenerateColumns, GridColumnCollection presentColumns, String[] additionalField, Boolean retrieveAllFields)
   at Telerik.Web.UI.GridDataSourceHelper.GetResolvedDataSource(GridTableView owner, Object dataSource, String dataMember, Boolean caseSensitive, Boolean autoGenerateColumns, GridColumnCollection presentColumns, String[] additionalField, Boolean retrieveAllFields)
   at Telerik.Web.UI.GridTableView.get_ResolvedDataSource()
   at Telerik.Web.UI.GridTableView.CreateChildControls(IEnumerable dataSource, Boolean useDataSource)
   at System.Web.UI.WebControls.CompositeDataBoundControl.PerformDataBinding(IEnumerable data)
   at System.Web.UI.WebControls.DataBoundControl.OnDataSourceViewSelectCallback(IEnumerable data)
   at System.Web.UI.DataSourceView.Select(DataSourceSelectArguments arguments, DataSourceViewSelectCallback callback)
   at System.Web.UI.WebControls.DataBoundControl.PerformSelect()
   at Telerik.Web.UI.GridTableView.PerformSelect()
   at System.Web.UI.WebControls.BaseDataBoundControl.DataBind()
   at Telerik.Web.UI.GridTableView.DataBind()
   at Telerik.Web.UI.RadGrid.DataBind()
   at Telerik.Web.UI.RadGrid.AutoDataBind(GridRebindReason rebindReason)
   at Telerik.Web.UI.RadGrid.OnLoad(EventArgs e)
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
   --- End of inner exception stack trace ---
   at System.Web.UI.Page.HandleError(Exception e)
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
   at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
   at System.Web.UI.Page.ProcessRequest()
   at System.Web.UI.Page.ProcessRequestWithNoAssert(HttpContext context)
   at System.Web.UI.Page.ProcessRequest(HttpContext context)
   at ASP.adm_default_aspx.ProcessRequest(HttpContext context)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

Event in codebehind:

        protected void pagesRadGrid_OnNeedDataSource(object source, GridNeedDataSourceEventArgs e)
        {
            LightSpeedContext<dbLightSpeedModelUnitOfWork> context = new LightSpeedContext<dbLightSpeedModelUnitOfWork>("Website");
            using (var unitOfWork = context.CreateUnitOfWork())
            {
                pagesRadGrid.DataSource = unitOfWork.WebsitePages;
            }
        }

Any ideas?

Thanks

This may be to do with the way that LINQ defers queries.  Recall that LightSpeedModelUnitOfWork.WebsitePages is an IQueryable, not an IList.  The Find is executed only when something enumerates that IQueryable.  Thus, if setting the DataSource property does not cause the grid to enumerate the results immediately, but instead the grid only consults the DataSource after it returns from the NeedDataSource event, that would cause your problem because the UOW has been eagerly disposed.

A couple of possible solutions:

* Force the enumeration explicitly: pagesRadGrid.DataSource = unitOfWork.WebsitePages.ToList();

* Use the "unit of work per request" pattern -- use the PerRequestUnitOfWorkScope class to create UOWs that last for the duration of the Web request.  See http://www.mindscape.co.nz/blog/index.php/2008/05/12/using-the-unit-of-work-per-request-pattern-in-aspnet-mvc/ (it's not specific to ASP.NET MVC, and note that the scope class is now built into LightSpeed).

As a heads up, a similar issue can arise with lazy loading of associations, though I don't think that is the problem in your case.

Hello!

Thanks for answering. So if I understand correctly: I must create PerRequestUnitOfWorkScope class, add LightSpeed context to Global.asax and then at the beggining of codebehind files for every page declare:

PerRequestUnitOfWorkScope<dbLightSpeedModelUnitOfWork> unitOfWork = new PerRequestUnitOfWorkScope<dbLightSpeedModelUnitOfWork>(Global.LightSpeedContext);

?

Thanks

 Actually now I have small problem. This is error I'm getting:

System.ArgumentException: Format of the initialization string does not conform to specification starting at index 0.

 Any ideas?

My mistake. I've removed PerRequestUnitOfWorkScope because it is already in Lightspeed and in Global.asax I've typed Connection string name instead of connection string. After changing it to

ConfigurationManager.ConnectionStrings["Website"].ConnectionString

everything works fine now (Telerik RadGrid is correctly databinded too).

Thanks for help.