We wrote a generic filterable repository in .NET 8 that should be able to accept a list of filters and a list of sorts, and apply them to any given entity.

Due to some business logic, we have a Task entity that needs to be grouped everytime it is filtered. The grouping ‘eats’ the sorts, and they never get applied, I checked the query that is executed. But we need to sort after the grouping, and then apply pagination.

The method looks like this:

public static (IQueryable Queryable, int TotalElements) BuildFilteredQuery(IQueryable queryable, List<FilterData> filters, List<SortData> sorts, int pageNo, int pageSize, bool distinct)
    {
        queryable = ApplyFilters(queryable, filters);
        queryable = ApplySorting(queryable, sorts);

        if (distinct)
        {
            queryable = queryable.GroupBy("new(CountSort)").Select("it.First()");
        }

        var totalElements = queryable.Count();

        if (pageSize != 0)
        {
            queryable = ApplyPaging(queryable, pageNo, pageSize);
        }

        return (queryable, totalElements);
    }

private static IQueryable ApplySorting(IQueryable queryable, List<SortData> sorts)
    {
        var sortingString = string.Join(", ", sorts.Select(s =>
            $"{s.PropertyName} {(s.Direction == ListSortDirection.Ascending ? "asc" : "desc")}"));

        if (!string.IsNullOrWhiteSpace(sortingString))
        {
            queryable = queryable.OrderBy(sortingString);
        }

        return queryable;
    }

If we try to apply the sorting after the grouping, we get “The given key ‘EmptyProjectionMember’ was not present in the dictionary”.