Virtualization and Grouping Quirk

bmccord · December 7, 2023, 8:46pm

I am converting a .Net Framework WPF app to a .Net 7 Blazor WASM app. If I specify grouping in a grid but not virtualization, it works fine. If I specify both grouping and virtualization it also works fine, except that when I undo the grouping it throws an error message: "Unhandled exception rendering component: Value cannot be empty. (Parameter 'ordering')". Other than the error message itself, everything works as I would wish.

I suspect that the problem may stem from the fact that I'm not using Entity Framework to fetch the data. Instead, I am using Rocky Lhotka's CSLA framework fronting ADO.Net access. Since CSLA produces collections that are IEnumerable and IQueryable, I can use an IQueryable connection rather than LoadData.

I note that the SortOrder parameter also has no effect, which may be a related symptom. However, I read in all the collections in the order that I want them displayed, so this presents no problem.

To sum up:

Without converting completely to EF, which is not an option, is there some way I can supply a DBContext to solve the problem?
Would switching to LoadData help?
Is there an easy way to suppress the message, which is actually the only part not working as I would wish?

enchev · December 8, 2023, 6:39am

Hi @bmccord,

I’ve never seen such error before with grouping and virtualization. Can you post the stack trace?

bmccord · December 8, 2023, 2:00pm

Microsoft.AspNetCore.Components.WebAssembly.Rendering.WebAssemblyRenderer[100]
Unhandled exception rendering component: Value cannot be empty. (Parameter 'ordering')
System.ArgumentException: Value cannot be empty. (Parameter 'ordering')
at System.Linq.Dynamic.Core.Validation.Check.NotNullOrWhiteSpace(String value, String parameterName)
at System.Linq.Dynamic.Core.Validation.Check.NotEmpty(String value, String parameterName)
at System.Linq.Dynamic.Core.DynamicQueryableExtensions.InternalOrderBy(IQueryable source, ParsingConfig config, String ordering, Object comparer, Object args)
at System.Linq.Dynamic.Core.DynamicQueryableExtensions.OrderBy(IQueryable source, ParsingConfig config, String ordering, Object args)
at System.Linq.Dynamic.Core.DynamicQueryableExtensions.OrderBy[PromotionTracking](IQueryable1 source, ParsingConfig config, String ordering, Object[] args) at System.Linq.Dynamic.Core.DynamicQueryableExtensions.OrderBy[PromotionTracking](IQueryable1 source, String ordering, Object args)
at Radzen.Blazor.RadzenDataGrid1.<LoadGroups>d__15[[StadisClasses.PromotionTracking, StadisClasses, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].MoveNext() at Microsoft.AspNetCore.Components.Web.Virtualization.Virtualize1[[System.Linq.Dynamic.Core.GroupResult, System.Linq.Dynamic.Core, Version=1.3.0.0, Culture=neutral, PublicKeyToken=0f07ec44de6ac832]].BuildRenderTree(RenderTreeBuilder builder)
at Microsoft.AspNetCore.Components.ComponentBase.<.ctor>b__6_0(RenderTreeBuilder builder)
at Microsoft.AspNetCore.Components.Rendering.ComponentState.RenderIntoBatch(RenderBatchBuilder batchBuilder, RenderFragment renderFragment, Exception& renderFragmentException)

enchev · December 8, 2023, 2:03pm

Looks like this code is casing the exception. Try to attach Radzen.Blazor project to your app to debug what's null/empty:

github.com

radzenhq/radzen-blazor/blob/master/Radzen.Blazor/RadzenDataGrid.razor.cs#L133


      
                  private async ValueTask<Microsoft.AspNetCore.Components.Web.Virtualization.ItemsProviderResult<GroupResult>> LoadGroups(Microsoft.AspNetCore.Components.Web.Virtualization.ItemsProviderRequest request)
                  {
                      var top = request.Count;
          
                      if(top <= 0)
                      {
                          top = PageSize;
                      }
          
                      var view = AllowPaging ? PagedView : View;
                      var query = view.AsQueryable().OrderBy(string.Join(',', Groups.Select(g => $"{(typeof(TItem) == typeof(object) ? g.Property : "np(" + g.Property + ")")}")));
                      _groupedPagedView = query.GroupByMany(Groups.Select(g => $"{(typeof(TItem) == typeof(object) ? g.Property : "np(" + g.Property + ")")}").ToArray()).ToList();
          
                      var totalItemsCount = await Task.FromResult(_groupedPagedView.Count());
          
                      return new Microsoft.AspNetCore.Components.Web.Virtualization.ItemsProviderResult<GroupResult>(_groupedPagedView.Skip(request.StartIndex).Take(top), totalItemsCount);
                  }
          #endif
          
                  RenderFragment DrawRows(IList<RadzenDataGridColumn<TItem>> visibleColumns)
                  {

bmccord · December 8, 2023, 2:56pm

If I'm reading that correctly, that's the code that sets up the grouping. My error is occurring when I UNDO the grouping by clicking on the X in the field cartouche. It undoes the grouping correctly, and goes back to the ungrouped grid, but it also throws the error message.

Are there instructions somewhere as to how to attach the Radzen.Blazor project? I'm a one man band here and haven't had occasion to connect to other people's code. I would prefer not to have to copy down all the source.

enchev · December 8, 2023, 3:05pm

Hey @bmccord,

Our components are free and open source - this is how the open source world works. If you do not want to debug the exception I'm afraid that I don't have any other ideas.

bmccord · December 8, 2023, 3:25pm

I think you may have misread my reply. Your suggestion to attach to your code and see what's happening is an excellent one. I was just saying that I don't have experience working on group projects and was unsure how to go about attaching to your code.

enchev · December 8, 2023, 3:49pm

You can remove Radze.Blazor dependency and attach Radzen.Blazor.csproj as project reference: