爲什麼我的代碼在每種情況下都將一個項目從列表中刪除？

Question

我正在研究此培訓視頻。我在下面的例子中注意到，我的代碼每次都會將最後一項留在列表之外。在我使代碼更加花哨和可讀性之前，它工作正常。

問題：爲什麼我的代碼離開最後一個項目？

SortedDictionary<string, SortedSet<Employee>> 

代碼：

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Text; 

namespace ConsoleApplication1 
{ 
    class Program 
    { 
     private void printDictionary(Dictionary<string, List<Employee>> InputDictionaryParm1) 
     { 
      foreach (var a in InputDictionaryParm1) 
      { 
       Console.WriteLine(a.Key); 
       foreach (var e in a.Value) 
       { 
        Console.WriteLine("\t" + e.Name); 
       } 
      } 
      Console.ReadKey(); 
     } 

     static void Main(string[] args) 
     { 
      var d = new DepartmentCollection(); 

      d.AddDept("AA", new Employee { Name = "L" }) 
      .AddDept("AA", new Employee { Name = "A" }); 

      d.AddDept("BB", new Employee { Name = "D" }) 
      .AddDept("BB", new Employee { Name = "E"}) 
      .AddDept("BB", new Employee { Name = "F"}) 
      .AddDept("BB", new Employee { Name = "A"}); 

      d.AddDept("CC", new Employee { Name = "J" }) 
      .AddDept("CC", new Employee { Name = "Z" }) 
      .AddDept("CC", new Employee { Name = "X" }) 
      .AddDept("CC", new Employee { Name = "Y" }); 

      d.AddDept("DD", new Employee { Name = "T" }) 
      .AddDept("DD", new Employee { Name = "W" }) 
      .AddDept("DD", new Employee { Name = "E" }) 
      .AddDept("DD", new Employee { Name = "A" }); 

      foreach (var a in d) 
      { 
       Console.WriteLine(a.Key); 
       foreach (var e in a.Value) 
       { 
        Console.WriteLine("\t" + e.Name); 
       } 
      } 
      Console.ReadKey(); 
      //printDictionary(d); 
     } 
    } 

    public class EmployeeComparer : IEqualityComparer<Employee>, 
            IComparer<Employee> 
    { 
     public EmployeeComparer() { } 

     public bool Equals(Employee x, Employee y) 
     { 
      return String.Equals(x.Name, y.Name); 
     } 

     public int GetHashCode(Employee obj) 
     { 
      return obj.Name.GetHashCode(); 
     } 

     public int Compare(Employee x, Employee y) 
     { 
      return String.Compare(x.Name, y.Name); 
     } 
    } 

    public class DepartmentCollection : SortedDictionary<string, SortedSet<Employee>> 
    { 
     public DepartmentCollection() 
     { 
      Console.WriteLine("DepartmentCollection"); 
     } 

     public DepartmentCollection AddDept(string d, Employee e) 
     { 
      if (ContainsKey(d)) 
      { 
       this[d].Add(e); 
      } 
      else 
      { 
       Add(d, new SortedSet<Employee>(new EmployeeComparer())); 
      } 
      return this; 
     } 
    } 
} 

屏幕截圖：

Answer 1

你AddDept方法實際上並沒有增加的值，如果鑰匙丟失：

public DepartmentCollection AddDept(string d, Employee e) 
    { 
     if (ContainsKey(d)) 
     { 
      this[d].Add(e); 
     } 
     else 
     { 
      Add(d, new SortedSet<Employee>(new EmployeeComparer())); 

      // Add this! 
      this[d].Add(e); 
     } 
     return this; 
    } 

請注意，您可以扭轉的條件簡化了這個代碼：

public DepartmentCollection AddDept(string d, Employee e) 
    { 
     if (!ContainsKey(d)) 
     { 
      Add(d, new SortedSet<Employee>(new EmployeeComparer())); 
     } 

     this[d].Add(e); 
     return this; 
    }