LINQ to SQL查詢乘兩列和計算SUM

Question

這裏的SQL查詢

Select sum(f.Acres*m.credit1), sum(f.Acres*m.credit2), sum(f.Acres*m.credit3) 
from first f join model m on f.Id = m.fID 
where m.year == 2012 

如何寫LINQ這上面的SQL？

謝謝！

Answer 1

這在Linq中有點棘手，因爲您需要一個組來完成聚合。通過對虛值，分組喜歡它下面會工作：

var q = from f in first 
     join m in model on f.Id equals m.fID 
     where m.year == 2012 
     group new { f, m } by 1 into g 
     select new 
     { 
      credit1 = g.Sum(x => x.f.Acres * x.m.credit1), 
      credit2 = g.Sum(x => x.f.Acres * x.m.credit2), 
      credit3 = g.Sum(x => x.f.Acres * x.m.credit3) 
     }; 

編輯
從閱讀您的意見。 如果你想讓它每年組，你這是怎麼做到這一點：

var q = from f in first 
     join m in model on f.Id equals m.fID 
     where m.year >= 2014 && m.year <= 2020 
     group new { f, m } by m.year into g 
     select new 
     { 
      year = g.Key, 
      credit1 = g.Sum(x => x.f.Acres * x.m.credit1), 
      credit2 = g.Sum(x => x.f.Acres * x.m.credit2), 
      credit3 = g.Sum(x => x.f.Acres * x.m.credit3) 
     };