LINQ-GroupBy項和基於兩個屬性的過濾器

Question

我有項目清單

var itema = new ObjX { Id = 1, MajorV = 1, MinorV = 1 };
var itemb = new ObjX { Id = 1, MajorV = 2, MinorV = 1 };
var itemc = new ObjX { Id = 1, MajorV = 3, MinorV = 0 };
var iteme = new ObjX { Id = 2, MajorV = 2, MinorV = 0 };
var itemf = new ObjX { Id = 2, MajorV = 2, MinorV = 1 };

我想創建一個linq查詢以返回唯一ids的列表，這些ids首先具有最高的MajorV ，然后具有最高的MinorV

在此示例中，要返回的項目為itemc和itemf 。

我有以下查詢，但未考慮MinorV

var filteredquery = query.GroupBy(cm => new { cm.Id })
                    .Select(grp => grp.Aggregate((max, cur) =>
                    (max == null || cur.MajorV > max.MajorV) ? cur : max));

有什么想法嗎？

Answer 1

var filteredquery = query.GroupBy(cm => cm.Id)
                .Select(gcm => gcm.OrderByDescending(cm => cm.MajorV).OrderByDescending(cm => cm.MinorV).First());

Answer 2

這給了我您期望的結果：

var result = items.GroupBy(x => x.Id)
                  .Select(x => 
                  {
                     var CriteriaObj = x.OrderByDescending(z => z.MajorV)
                                        .ThenByDescending(z => z.MinorV).First();
                     return new ObjX
                            {
                                Id = x.Key,
                                MajorV = CriteriaObj.MajorV,
                                MinorV = CriteriaObj.MinorV
                            };
                  }).ToList();

工作小提琴。

Answer 3

基於Dmitry Bychenko答案和Stefan Steinegger的評論，此查詢最簡單且有效：

       var filteredquery = query
                           .GroupBy(x => x.Id)
                           .Select(chunk => chunk
                               .OrderByDescending(item => item.MajorV)
                               .ThenByDescending(item => item.MinorV)
                               .First())
                           .ToList();