Error with returning IQueryable object from application service #9497

15 Answer(s)

• 

  0

  AI-Bot created 19 days ago

  Support Team ABP Agent

  The error occurs because returning IQueryable<T> directly from an ABP application service (or any Web API) is not supported. IQueryable is an interface and cannot be serialized/deserialized over HTTP, which is why you see the "could not be instantiated and populated" exception. ABP's dynamic HTTP API client and System.Text.Json cannot handle IQueryable<T> as a return type.

  To work with large datasets in Blazor (including DevExpress or other grids), you should implement server-side paging, sorting, and filtering in your application service. Instead of returning IQueryable<T>, return a paged result (such as a List<T> or a PagedResultDto<T>) from your application service.

  Example:

  public async Task<PagedResultDto<DataDictionaryDto>> GetListAsync(PagedAndSortedResultRequestDto input)
  {
      var query = _dataDictionaryRepository
          .WhereIf(!input.Filter.IsNullOrWhiteSpace(), x => x.Name.Contains(input.Filter));
      var totalCount = await query.CountAsync();
      var items = await query
          .OrderBy(input.Sorting ?? "Name")
          .Skip(input.SkipCount)
          .Take(input.MaxResultCount)
          .ToListAsync();
  
      return new PagedResultDto<DataDictionaryDto>(totalCount, ObjectMapper.Map<List<DataDictionary>, List<DataDictionaryDto>>(items));
  }
  

  On the Blazor client, use the grid's "load data" event to call this paged API and bind the result.

  This is the recommended and supported approach in ABP for large data grids.

  No verified source available for this specific query.

  ---

  This response was generated by AI. If it didn’t solve your problem, feel free to post a new answer — our support team will jump in to help you soon.

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• 

  0

  Spospisil created 16 days ago

  I've adjusted my solution as was suggested and while I do not get the error I was once getting the grid still does not load the grid with the first 20 rows of the dataset and allow me to page to the next 20, etc. As I mentioned in my initial ticket, we are using DevExpress datagrid not the Blazorise grid.

  I have updated the git repo with the implemented suggestion

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• 

  0

  maliming created 16 days ago

  Support Team Fullstack Developer

  hi

  Any idea what the underlying problem is and how I can fix it? I've given access to the private repository with a sample project to @maliming

  Where is your repository?

  Thanks.

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• 

  0

  Spospisil created 16 days ago

  ? You accepted the invite to git repo already.

  https://github.com/spospisil/AbpGridSolution

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• 

  0

  maliming created 16 days ago

  Support Team Fullstack Developer

  hi

  I asked the question URL https://github.com/spospisil/AbpGridSolution/issues/1

  Can you get DataDictionaryList in your blazor page now?

  var result = await DataDictionaryAppService.GetListAsync(input);
  DataDictionaryList = (List<DataDictionaryDto>)result.Items;
  

  If so, the backend is working. You can check DevExpress document to show the data.

  I don't have much experience with DevExpress.

  Thanks.

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• 

  0

  Spospisil created 16 days ago

  Your questions don't make sense!!! You have the support ticket URL because you are replying to me on it right now!!!!

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• 

  0

  maliming created 16 days ago

  Support Team Fullstack Developer

  hi

  I received an invitation from GitHub, but I don't know the question URL. There are many questions on the support website.

  ---

  Can you get DataDictionaryList in your blazor page now?

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• 

  0

  Spospisil created 16 days ago

  ? Maliming. You are replaying to the support ticket now!!!!!! My issue I'm having is at the top!!!!!! Why would the datadictionarylist work now? Did you make any changes to the code to get it to work?

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• 

  0

  maliming created 16 days ago

  Support Team Fullstack Developer

  hi

  What I mean is, I had no idea three days ago.

  If you invite me again later, please provide the URL for the support question.

  

  

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• 

  0

  Spospisil created 16 days ago

  OMG!!!!! But you know now right? What is unclear to you? You have the support ticket url (because you're replying to it) and you have access to the source code? Why are you confused?

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• 

  0

  maliming created 16 days ago

  Support Team Fullstack Developer

  You've already modified the code based on the AI's response so that the System.NotSupportedException: The collection type 'System.Linq.IQueryable error no longer appears.

  My question is: can you get the data returned by the application service on your blazor page?

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• 

  0

  maliming created 15 days ago

  Support Team Fullstack Developer

  Spospisil :No, I still cannot get data returned to the blazor page because now I'm encountering this error. I have changed the MaxResultCount and MaxMaxResultCount properties in several ways and I'm still getting this error. I have 50,000 rows in my database table and I'm trying to return all of them (for performance testing reasons) and it keeps popping up with the below error.

  Can you tell me what's wrong with the sample project's code?

  

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• 

  0

  maliming created 15 days ago

  Support Team Fullstack Developer

  hi

  You can increase LimitedResultRequestDto.MaxMaxResultCount number.

  

  See https://abp.io/docs/latest/framework/architecture/domain-driven-design/data-transfer-objects#max-result-count

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• 

  0

  maliming created 15 days ago

  Support Team Fullstack Developer

  hi

  I pushed my changes. https://github.com/spospisil/AbpGridSolution/pull/2

  1.The [RemoteService(IsEnabled = false)] need to be removed. 2. Application service can't return Task<IQueryable<DataDictionaryDto>> , Blazor will use ajax to get data. It doesn't support IQueryable, Blazor is a pure UI project.

  Now API can return the data.

  

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• 

  0

  Spospisil created 14 days ago

  Hi,

  Ended up going a different route to implement large dataset retrieval and loading into the DevExpress Blazor grid based on the great advice of the DevExpress support team. They responded with a comprehensive explanation of their product with regards to what I was trying to accomplish. Great support folks there for sure.

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