Apply Distinct in specification query

[Mohammad Ahmadi]

I have problem with this query I have multiple repeated data from query!

public class DataSetGetByFilterProjectsResultSpec : Specification<DataSet, ProjectViewDto>
  {
    public DataSetGetByFilterProjectsResultSpec(DataSetFilter filter)
    {
      Query
        .ApplyFiltering(filter);
  
      Query
        .Where(w => w.ProjectId.HasValue)
        .Include(c => c.Project)
        ;
  
      Query
        .Select(ds => new ProjectViewDto(ds.ProjectId!.Value, ds.Project!.Name));
    }
  }   
 
 var availableProjects = await _repository.ListAsync(new DataSetGetByFilterProjectsResultSpec(filter), ct);
  Response.Projects = availableProjects.Distinct().ToList();

[Fati Iseni]

Hi @mhd-ahmadi,

I don't think this has to do with this library. You're fetching data from the database, and then applying Distinct to an in-memory collection. The reason it's not working is because the Distinct LINQ method uses the Equals method to compare the objects. If your model ProjectViewDto is a class, then of course it won't work. You should override the Equals method, or more simply just use record instead of class.