LINQ查詢從使用包含GROUP BY和COUNT的子查詢的SQL進行轉換

Question

首先，如果之前已經詢問過此問題，但我已嘗試通過此處（幾天）搜索幾十個問題並且找不到合適的問題表示歉意。

我想將常見的SQL查詢翻譯成LINQ。下面是一個簡單的代碼版本，如果我能夠使用SQL語句...

List<T> myData = new List<T>(); // (Employee, Age, Department); 
myData.Add("Bill", 34, "IT"); 
myData.Add("Fred", 23, "ACCOUNTS"); 
myData.Add("Jane", 44, "SALES"); 
myData.Add("Sally", 56, "IT"); 
myData.Add("Harry", 33, "ACCOUNTS"); 


List<T> filteredData = SELECT * FROM myData 
           WHERE Department IN (
           SELECT Department 
           FROM myData 
           GROUP BY Department 
           HAVING (COUNT(Department) > 1) 
           ) 
         ORDER BY Department, Employee 

So that filteredData contains: 
          Fred, 23, ACCOUNTS 
          Harry, 33, ACCOUNTS 
          Bill, 34, IT 
          Sally, 56, IT 

這需要產生包含有一個以上的工作人員部門內工作人員名單。

任何人都可以將這個需求轉換成LINQ，Linq格式和使用方法（擴展名？）格式嗎？

Answer 1

這應該工作太：

var filteredData = myData.GroupBy(x => x.Department) 
         .Where(x => x.Count() > 1) 
         .SelectMany(x => x) 
         .OrderBy(x => x.Department) 
         .ThenBy(x => x.Employee) 
         .ToList(); 

Answer 2

這裏是抽象數據類：

public class Emp 
     { 
      public string Employee { get; set; } 
      public string Age { get; set; } 
      public string Department { get; set; } 
     } 

，這是通過做組所需的LINQ：

private void button1_Click(object sender, EventArgs e) 
      { 

     List<Emp> myData = new List<Emp>(); // (Employee, Age, Department); 
        myData.Add(new Emp{Employee = "Bill",Age ="34",Department = "IT"}); 
        myData.Add(new Emp { Employee = "Fred", Age = "23", Department = "ACCOUNTS" }); 
        myData.Add(new Emp { Employee = "Jane", Age = "44", Department = "SALES" }); 
        myData.Add(new Emp { Employee = "Sally", Age = "56", Department = "IT" }); 
        myData.Add(new Emp { Employee = "Harry", Age = "33", Department = "ACCOUNTS" }); 

        var results = from p in myData 
         group p by p.Department into g 
         select new { Department = g.Key, Result = g.Count() }; 

        var filteredData = myData.Where(x => results.Where(y => y.Result > 1).Select(z=> z.Department).Contains(x.Department)).OrderBy(em=> em.Department).ThenBy(em2=> em2.Employee).ToList(); 
    } 

更多關於的GroupBy是如何工作的，請參閱喬恩斯基特的post on the topic。