在LINQ中对多个独立列求和

本文关键字：独立 求和 LINQ | 更新日期: 2023-09-27 18:15:07

有人知道如何正确有效地对多个列求和吗?

我有一个庞大的连接查询

db.myTable.Join(...)
.Join(...)
.Join(...)
.Join(...)
.Join(...)
.Join(...)
.Where(...)

我现在需要做的是sum列A, B, C和d和Count e

所以我有一个记录，里面有总和

我尝试使用group by和Select(x => new myClass{A => x.})

下面是MAJORLY efficient

myClass mine = new myClass{ 
            Number = myList.GroupBy(x => x.u.ID).Count(),
            Area = myList.Sum(a => a.u.Area ?? 0),
            Rent = myList.Sum(a => a.r.Rent ?? 0)   ,
            ERV = myList.Sum(a => a.e.ERV ?? 0)
        };

下面是有效率的，但只对第一组求和…

      myClass mine = (from p in myList
                            group p by p.u.ID into g
                            select  new myClass
                            { 
                                Number = g.Count(),
                            Area = g.Sum(a => a.u.Area ?? 0),
                            Rent = g.Sum(a => a.r.Rent ?? 0)   ,
                            ERV = g.Sum(a => a.e.ERV ?? 0)
        }).FirstOrDefault();

在LINQ中对多个独立列求和

我认为您正试图获得数字字段的Distinct Count()与未分组的 Sum()在单个记录中的其他字段。

var mine = (from x in (from p in mc 
                       group p by p.u.id into g1
                       select new { 
                             Number = g1.Count(),
                             Area = g1.Sum(a => a.u.Area??0),
                             Rent = g1.Sum(a => a.u.Rent??0),
                             ERV = g1.Sum(a => a.e.ERV ?? 0)
                       })
                    group x by 1 into g2
                    select new myClass {
                             Number = g2.Count(),
                             Area = g2.Sum(a => a.Area),
                             Rent = g2.Sum(a => a.Rent),
                             ERV = g2.Sum(a => a.ERV)
                    }).FirstOrDefault();
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