Grid error "Must be reducible node" when i use aggregates

[Marco]

Hy,

I created a generic class for telerik grids to manage different data models.

In this class I use OnRead event for reading data :

 protected async Task OnReadHandlerAsync(GridReadEventArgs args)
 {
     try
     {
         var query = Service.QueryDto();
         query = DefaultFilterCondition is not null ? query.Where(DefaultFilterCondition) : query;
         var dataSourceResult = await query.ToDataSourceResultAsync(args.Request);
         if (args.Request.Aggregates.Any())
         {
             args.AggregateResults = dataSourceResult.AggregateResults;
         }
         args.Data = dataSourceResult.Data;
         args.Total = dataSourceResult.Total;
     }
     catch (Exception ex)
     {
         NotificationService.Error(ex.Message);
     }
 }

As you can see I use the ToDataSourceResult extension on a variable of type IQueryable<TDto> for automatic sorting, filtering,paging,...

But now I have a problem: I created a grid that contains aggregates, now for this TelerikGrid the application throws the "must be reducible node exception" when the "ToDataSourceResult" is executed on the IQueyable<TDto> variable. 

My TelerikGrid with aggregates:

@inherits GridReadOnlyComponentBase<SimulationResultService,SimulationResultDto>
<TelerikGrid Id="simulationresultgrid"
             @ref="GridRef"
             TItem="SimulationResultDto"             
             OnStateInit="@OnStateInitHandler"
             FilterMode="@GridFilterMode.FilterRow"
             EditMode="@GridEditMode.None"
             SelectionMode="@GridSelectionMode.None"             
             Sortable="@true" SortMode="@SortMode.Single"
             Groupable="@true" LoadGroupsOnDemand="@false"
             Reorderable="@false"                                                                 
             OnRead="@OnReadHandlerAsync">

     <GridAggregates>
        <GridAggregate Field="@nameof(SimulationResultDto.ActualSales)" Aggregate="@GridAggregateType.Sum" FieldType="typeof(decimal)" />
        <GridAggregate Field="@nameof(SimulationResultDto.YearImpact)" Aggregate="@GridAggregateType.Sum" FieldType="typeof(decimal)" />
        <GridAggregate Field="@nameof(SimulationResultDto.ChangesImpact)" Aggregate="@GridAggregateType.Sum" FieldType="typeof(decimal)" />
    </GridAggregates> 

    <NoDataTemplate>
        <strong>@(_simulationId > 0 ? "Nessun dato presente,eseguire prima una simulazione" : "Scegli la simulazione")</strong>
    </NoDataTemplate>

    <GridToolBarTemplate>
        <span class="k-toolbar-spacer" />
        <SimulationSelect SelectedValue="_simulationId" SelectedValueChanged="SimulationIdChanged" Width="30%" />
    </GridToolBarTemplate>

    <GridColumns>        
        <GridColumn Field="@nameof(SimulationResultDto.ActualSales)"
                    Title="Fat. attuale"
                    Width="200px" DisplayFormat="{0:C}"
                    Filterable="false"
                    Groupable="false">
             <GroupFooterTemplate>
                TOT: <TelerikNumericTextBox Width="80%" ReadOnly="@true" Arrows="@false" Decimals="2" Format="C" @bind-Value="@context.Sum" />
            </GroupFooterTemplate> 
        </GridColumn>        
    </GridColumns>

I know that a solution could be to run the ToList before running the ToDataSourceResult but I would like to know if there is another solution as I work with a large amount of data.

Thanks

[Svetoslav Dimitrov]

Hello Marko,

This exception seems to be connected to a bug in Entity Framework Core 2.1.1 and is logged in their public GitHub repository. As you rightfully said, a fix is to use the ToList() method or downgrade to the 2.0 version of Entity Framework Core. 

If you are not using EF Core, I would like to request a runnable solution where the issue is reproducible so that we can investigate properly. 

Regards,
Svetoslav Dimitrov
Progress Telerik

[Marco]

Hy Dimitrov,

Yes, I'm currently using the last version of the Entity Framework Core package (8.0.5). 

The downgrade of the Entity Framework Core is not a solution i can use, nor is the ToList() method because i work with tables that contain a large number of elements and I need to optimize calls to my Db. 

For example, in a grid with pagination as well, I would like to call the Db for only the elements of the current page, after filtering, grouping,sorting.. 

So, if i understand correctly, the only solution I have is to manually create all the operations in the OnRead event,using the ToList() method only after pagination (Skip() and Take())?

Thanks in advance,

Marco

[Svetoslav Dimitrov]

Hello Marco,

It seems that Microsoft believes that this issue is by design. They marked the issue with the closed-by-design label. That being said, this is beyond our control and the workaround remains the same.