linq分组和排序

Question

我有一个客户名单，我需要根据业务规则对列表进行排序和分组。

• 组由客户名称
• 排序按字母顺序
• 如果有相同名称的几个结果，那么就需要通过出生日期进行升序排序（最老的上市客户名称第一个）

下面是实体。

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

在此先感谢。

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

Answer 1

你的业务规则是有点矛盾的： Group by Customer Name意味着你不会有相同的名字多次出现在结果列表中。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。所以，如果在规则＃1分组你的意思是排序，您的查询将仅仅是：

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

如果你真正的意思是分组规则＃3成为标准组中选择元素 - 在这种情况下，最早的客户将选择对于每个组：

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

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); 

Answer 3

这似乎有点奇怪，以客户的名义组，但是这将做到这

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;