Question

我有一个客户列表，我需要根据业务规则对列表进行排序和分组。

按客户名称分组
按字母顺序按客户名称排序
如果有多个相同名称的结果，那么他们需要按出生日期按升序排序（最早列出的是最早的）

以下是实体。

public class Customer
{
 public string FirstName {get; set;}
 public string LastName {get; set;}
 public DateTime DateofBirth {get; set;}
}

提前致谢。

customers.GroupBy(c => c.FirstName)
.Select(c => c.OrderBy(c => c.FirstName).ThenBy(c => c.LastName));

Answer 1

您的业务规则有些矛盾： Group by Customer Name表示您不会在结果列表中出现多次相同名称。然而你的第三条规则是if there are several results for the same name, then they need to sorted by date of birth。因此，如果通过在规则＃1中进行分组，则意味着排序，您的查询将仅仅是：

customers.OrderBy(c => c.FirstName).
          ThenBy(c => c.LastName).
          ThenBy(c => c.DateofBirth);

如果您实际上是指分组，则规则＃3成为选择组中元素的标准 - 在这种情况下，将为每个组选择最早的客户：

customers.GroupBy(c => c.FirstName + c.LastName).
          Select(g => g.OrderBy(c => c.DateofBirth).FirstOrDefault()).
          OrderBy(c => c.FirstName).
          ThenBy(c => c.LastName);

Answer 2

对客户名称进行分组似乎有点奇怪，但这样做

var groups = from c in customers 
                let name = c.FirstName + " " + c.LastName
                orderby name ascending, c.DateofBirth ascending
                group c by name into g
                select g;

Answer 3

var sortList = (from c in customers
                             group c by new 
                             { 
                                 c.FirstName, 
                                 c.LastName, 
                                 c.DateofBirth 
                             } into g
                             select new Customer()
                             { 
                                 FirstName = g.Key.FirstName, 
                                 LastName = g.Key.LastName, 
                                 DateofBirth = g.Key.DateofBirth 
                             }).OrderBy( x => x.FirstName )
                             .ThenBy( x=> x.LastName)
                             .ThenBy(x=> x.DateofBirth);

分组＆amp;在linq中排序

3 个答案: