linq分組和排序

Question

我有一個客戶名單，我需要根據業務規則對列表進行排序和分組。

• 組由客戶名稱
• 排序按字母順序
• 如果有相同名稱的幾個結果，那麼就需要通過出生日期進行升序排序（最老的上市客戶名稱第一個）

下面是實體。

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

在此先感謝。

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

Answer 1

你的業務規則是有點矛盾的： Group by Customer Name意味着你不會有相同的名字多次出現在結果列表中。然而你的第三條規則是if there are several results for the same name, then they need to sorted by date of birth。所以，如果在規則＃1分組你的意思是排序，您的查詢將僅僅是：

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

如果你真正的意思是分組規則＃3成爲標準組中選擇元素 - 在這種情況下，最早的客戶將選擇對於每個組：

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

這似乎有點奇怪，以客戶的名義組，但是這將做到這

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;