Question

我想只获得最大的StartDate，它的日期倍数与相同的CustomNumber

有什么建议吗？

我的简化代码

from Cus in Customers
where Cus.CustomNumber == 2 
group Cus by new 
 { Cus.Name,Cus.City,Cus.StartDate}
 into grp
 select new 
 {
    Name = grp.Key.Name,
    City = grp.Key.City, 
    StartDate = grp.Key.StartDate,

    //I have tried, but it doesnt work for me
    //StartDate = grp.Max(Cus=> grp.Key.StartDate)
 }

Answer 1

你可以尝试这个：

var result = from Cus in Customers
             where Cus.CustomNumber == 2 
             group Cus by new 
             { Cus.Name, Cus.StartDate}
             into grp
             select new 
             {
                 Name = grp.Key.Name,
                 StartDate = grp.Max(x=>x.StartDate)
             };

使用grp您可以访问您在linq查询中创建的随机组，然后使用名为Max的扩展方法获得组中的最大StartDate。

<强>更新

由于您现在在分组之前有联接，您必须将代码更改为以下代码：

var result = from res in 
             (from customer in Customers
             join house in Houses 
             on customer.CustomNumber equals house.CustomNumber
             where customer.CustomNumber == 2               
             select new { Name = customer.Name, StartDate = house.StartDate })
             group res by res.Name into grp
             select new { Name = grp.Key, StartDate = grp.Max(x=>x.StartDate) };

更新＃2

如果您希望在结果中同时获得客户的姓名和城市，则必须使用以下代码：

var result = from res in 
             (from customer in Customers
             join house in Houses 
             on customer.CustomNumber equals house.CustomNumber
             where customer.CustomNumber == 2               
             select new { Name = customer.Name, City = customer.Name, StartDate = house.StartDate })
             group res by new { res.Name, res.City } into grp
             select new 
             { 
                 Name = grp.Key.Name, 
                 City = grp.Key.City,  
                 StartDate = grp.Max(x=>x.StartDate) 
             };

Answer 2

尝试以下代码

StartDate = grp.Max(x => x.StartDate)

如何在Linq中选择Max StartDate

2 个答案: