为什么我的代码在每种情况下都将项目从清单中剔除？

Question

我正在制作此培训视频。 我在下面的示例中注意到，我的代码每次都将最后一项保留在列表之外。 在我使代码更加精美和易读之前，它已经奏效。

问题：为什么我的代码保留最后一项？

SortedDictionary<string, SortedSet<Employee>>

码：

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;
        }
    }
}

屏幕截图：

Answer 1

如果缺少键，则您的AddDept方法实际上不会添加值：

    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;
    }

请注意，您可以反转条件以简化此代码：

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

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