Question

我正在尝试将linq查询与另一个表联系起来。如何在Customer表中显示名称？我收到错误：不包含“姓名”的定义？

   from p in Purchases 
join c in Customers on p.CustomerID equals c.ID
group p by p.Date.Year into SalesPerYear
select new {
customername= SalesPerYear.First().Name,
customerid= SalesPerYear.First().CustomerID,
totalsales= SalesPerYear.Sum(x=>x.Price)
}

Answer 1

您按日期对p（即购买）进行分组 - 因此客户详细信息不再存在。

请改为尝试：

from p in Purchases 
join c in Customers on p.CustomerID equals c.ID
group new { p, c } by p.Date.Year into SalesPerYear
select new {
    CustomerName = SalesPerYear.First().c.Name,
    CustomerId = SalesPerYear.First().p.CustomerID,
    TotalSales = SalesPerYear.Sum(x => x.p.Price)
}

或者：

from p in Purchases 
join c in Customers on p.CustomerID equals c.ID
group new { p.CustomerId, p.Price, c.CustomerName } 
   by p.Date.Year into SalesPerYear
select new {
    SalesPerYear.First().CustomerName,
    SalesPerYear.First().CustomerId
    TotalSales = SalesPerYear.Sum(x => x.Price)
}

Answer 2

SalesPerYear是一个IGrouping。您需要从IGrouping的Value属性访问Name，CustomerID等。

linq表达错误：无法显示列？

2 个答案: