使用分组依据的LINQ性能优化

Question

I've a group by clause in C# LINQ, it's taking more than 5 minutes to execute. In production environment timing out because of large scale data. Is there any way to optimize this LINQ query ? Appreciate any help.

var qFilingReview = (from x in FilingReviewsList
                    group x by new { x.filingAnswer.Grouping, x.filingAnswer.Instructions, x.filingReview.Name, x.filingQuestion.Number } into grp
                    select new { result = grp.FirstOrDefault() })
                         .ToList()
                         .OrderBy(k => k.result.filingQuestion.Id)
                         .ThenByDescending(k => k.result.filingAnswer.Id);

Answer 1

首先，我认为您必须删除不必要的ToList（）调用。