Round #792

Write a self-join to find pairs of employees with the same manager.

```csharp using System; using System.Data; using System.Linq; public class Employee { public int Id { get; set; } public string Name { get; set; } public int ManagerId { get; set; } } class Program { static void Main() { // Create a sample DataTable var employees = new[] { new Employee { Id = 1, Name = "John", ManagerId = 101 }, new Employee { Id = 2, Name = "Alice", ManagerId = 101 }, new Employee { Id = 3, Name = "Bob", ManagerId = 102 }, new Employee { Id = 4, Name = "Mary", ManagerId = 103 }, new Employee { Id = 5, Name = "Peter", ManagerId = 101 }, }; // Perform a self-join to find pairs of employees with the same manager var pairs = from e1 in employees from e2 in employees where e1.ManagerId == e2.ManagerId && e1.Id < e2.Id select new { Employee1 = e1.Name, Employee2 = e2.Name }; // Print the pairs foreach (var pair in pairs) { Console.WriteLine($"{pair.Employee1} and {pair.Employee2} have the same manager."); } } } ```

```csharp using System; using System.Data; using System.Data.SqlClient; public class Employee { public int Id { get; set; } public string Name { get; set; } public int ManagerId { get; set; } } public class Program { public static void Main() { // Create a sample DataTable DataTable employees = new DataTable(); employees.Columns.Add("Id", typeof(int)); employees.Columns.Add("Name", typeof(string)); employees.Columns.Add("ManagerId", typeof(int)); employees.Rows.Add(1, "John", 101); employees.Rows.Add(2, "Alice", 101); employees.Rows.Add(3, "Bob", 102); employees.Rows.Add(4, "Charlie", 102); employees.Rows.Add(5, "David", 103); // Perform self-join to find pairs of employees with the same manager var pairs = from e1 in employees.AsEnumerable() join e2 in employees.AsEnumerable() on e1.Field<int>("ManagerId") equals e2.Field<int>("ManagerId") where e1.Field<int>("Id") < e2.Field<int>("Id") select new { Employee1 = e1.Field<string>("Name"), Employee2 = e2.Field<string>("Name") }; // Print the pairs foreach (var pair in pairs) { Console.WriteLine($"{pair.Employee1} and {pair.Employee2} have the same manager."); } } } ``` This C# code performs a self-join on a DataTable of employees to find pairs of employees with the same manager. The self-join is done using LINQ, and the results are printed to the console. The `where` clause ensures that each pair is only listed once, by only considering pairs where the first employee's ID is less than the second employee's ID.