protected virtual async Task <IQueryExecutionResult> ExecuteAsyncGrouping <T>(CancellationToken cancellationToken)
{
var result = new QueryExecutionResult();
// preserve queryable.
var queryableAfterFilters = CurrentQueryable;
// async.
result.TotalRecords = await this.AsyncQueryableService.LongCountAsync((IQueryable <T>) queryableAfterFilters, cancellationToken);
CalculatePageCount(result);
// intercept groups in advance to avoid doing it more than once :)
var finalGroups = Criteria.Groups.Select(g => InterceptGroup <T>(g)).ToList();
// get the aggregates.
var aggregateResults = await FetchAggregatesAsync <T>(finalGroups, cancellationToken);
// sorting.
finalGroups.ForEach(fg => Criteria.Sorts.Insert(0, new Sort(fg.Path, fg.Ascending)));
// apply sorting and paging.
ApplySorting <T>();
ApplyPaging <T>();
// create group & select expression.
CurrentQueryable = CurrentQueryable.GroupBy(QueryableUnderlyingType, gb => finalGroups.ForEach((fg, index) => gb.Path(fg.Path, $"Key_{index}")));
CurrentQueryable = CurrentQueryable.Select(sb =>
{
finalGroups.ForEach((fg, index) => sb.Key($"Key_{index}", $"Key_{index}"));
sb.ToList("Records");
});
// loop through the grouped records.
// var groupRecords = await AsyncQueryableService.ToListAsync(CurrentQueryable.Cast<DynamicClass>(), cancellationToken);
// now join them into logical collections
// result.Data = RecursiveRegroup<T>(groupRecords, aggregateResults, Criteria.Groups.First());
result.Data = CurrentQueryable;
result.Aggregates = await CalculateTotalAggregateAsync <T>(queryableAfterFilters, cancellationToken);
return(result);
}