Linq多列分组和平均

Question

我试图得到分组后的一些数字的平均值，但它不会为我分组。为什么这不是我认为应该做的？

var eventInfo = from eventData in dt.AsEnumerable() 
    group eventData by new 
     { 
      Phase1Minutes = eventData.Field<decimal>("Phase1Minutes"), 
      Phase2Minutes = eventData.Field<decimal>("Phase2Minutes"), 
      TechnologyType = eventData.Field<string>("TechnologyType"), 
      TechnologySubType = eventData.Field<string>("TechnologySubType") 
     } into g 
    select new 
    { 
     Phase1Avg = g.Average(x => x.Field<decimal>("Phase1Minutes")), 
     Phase2Avg = g.Average(x => x.Field<decimal>("Phase2Minutes")), 
     g.Key.TechnologyType, 
     g.Key.TechnologySubType 
    }; 

Answer 1

根据你已经分组的内容进行平均是没有意义的。只是举一个微不足道的例子，想象一下按年龄分组人群，然后找出每个组中的平均年龄......他们都是同一个年龄段！

我的猜测是，你只需要取出分组的部分分：

var eventInfo = from eventData in dt.AsEnumerable() 
    group eventData by new 
     { 
      TechnologyType = eventData.Field<string>("TechnologyType"), 
      TechnologySubType = eventData.Field<string>("TechnologySubType") 
     } into g 
    select new 
    { 
     Phase1Avg = g.Average(x => x.Field<decimal>("Phase1Minutes")), 
     Phase2Avg = g.Average(x => x.Field<decimal>("Phase2Minutes")), 
     g.Key.TechnologyType, 
     g.Key.TechnologySubType 
    };