我需要将 sql 转换为 Linq

Question

这是我的 sql 命令：

select 
    b.Brand, 
    count(b.Brand) as BrandCount,
    SUM(a.Qty) as DeviceCount 
from (
    select * from DeviceList
) as a 
join DeviceMaster as b 
    on a.DeviceMasterId = b.Id
group by b.Brand

这是我到目前为止尝试过的方法：

var v1 = (from p in ghostEntities.DeviceMasters 
          join c in ghostEntities.DeviceLists on p.Id equals c.DeviceMasterId 
          select new table_Model { 
            Id = c.Id, 
            qty = c.Qty.Value, 
            month = c.DMonth, 
            brand = p.Brand, 
            model = p.Model, 
            memory = p.Memory
          }).ToList();

我正在从两个表中获取值，但无法对它们进行分组或添加值。

Answer 1

您应该将 group by 添加到 LINQ 查询中并使用 Distinct().Count() 和 Sum() 聚合函数：

var query = from a in ghostEntities.DeviceList
   join b in ghostEntities.DeviceMaster on a.DeviceMasterId equals b.Id
   group b by b.Brand into g
   select new { g.Key, count =g.Select(x => x.Brand).Distinct().Count(), sum = g.Sum(x => x.Qty) };

您可以在 https://code.msdn.microsoft.com/101-LINQ-Samples-3fb9811b 找到很多 LINQ 示例，希望对您有所帮助。

Answer 2

按 table 分组后，您将无法在连接操作中访问另一个 table 的字段，可能的解决方法是:

var results = (from a in DeviceList
                join b in DeviceMaster
                on a.DeviceMasterId equals b.Id
                group new { a, b } by new { b.Brand } into grp
                select new
                {
                    Brand = grp.Key.Brand,
                    BrandCount = grp.Count(),
                    DeviceCount = grp.Sum(x=> x.a.Qty.GetValueOrDefault())
                }).ToList();

我需要将 sql 转换为 Linq

I need to convert sql to Linq

c#

sql

linq

sql-to-linq-conversion