Select EF 6 Net Core 5 中 GroupBy 的 Min()

Question

在按“RateClass”分组的 table 中，我尝试 select“RateClass”、Min(“CostDay”) 和“CostWeek”，但我的代码崩溃了。

var data = db.Rates.GroupBy(t => t.RateClass)
             .Select( g => new {  
                                rateClass = g.Select(x => x.RateClass), 
                                costtDay = g.Min(x => x.CostDay), 
                                costWeek = g.Select(x => .CostWeek)
                               })
              .ToList();

Answer 1

正如我在评论中所述，它不会编译，因为你在这里缺少 x costWeek = g.Select(x => .CostWeek)，应该是 costWeek = g.Select(x => x.CostWeek)

此外，您是否尝试为每个组创建一个条目？如果是这样，你可以试试这个...

 public class Rates
    {
        public string RateClass { get; set; }
        public decimal CostDay { get; set; }
        public decimal CostWeek { get; set; }
    }


 var rates = new List<Rates>
            {
                new Rates {CostDay = 2, CostWeek = 7, RateClass = "Test 1"},
                new Rates {CostDay = 4, CostWeek = 17, RateClass = "Test 1"},
                new Rates {CostDay = 6, CostWeek = 27, RateClass = "Test 2"},
                new Rates {CostDay = 8, CostWeek = 37, RateClass = "Test 2"}
            };

            var data = rates.GroupBy(t => t.RateClass)
                .Select(g => new Rates {
                    RateClass = g.Key,
                    CostDay = g.Min(x => x.CostDay),
                    CostWeek = g.Sum(x => x.CostWeek)
                })
                .ToList();

RateClass 将是您分组的关键，我只是以 CostWeek 为例进行总结。这里有一个 link 可以试试。

Select EF 6 Net Core 5 中 GroupBy 的 Min()

Select Min() on GroupBy in EF 6 Net Core 5

sql

entity-framework-6

.net-core