LINQ to SQL查询乘两列和计算SUM

Question

这里的SQL查询

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 

如何写LINQ这上面的SQL？

谢谢！

Answer 1

这在Linq中有点棘手，因为您需要一个组来完成聚合。通过对虚值，分组喜欢它下面会工作：

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) 
     }; 

编辑
从阅读您的意见。 如果你想让它每年组，你这是怎么做到这一点：

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) 
     };