C#實現IDictionary接口

C#實現IDictionary接口

最近學習.Net開發，發現自己跟着實現一個微軟官方文檔的例子，對自己理解一些相關的數據結構和用法有相當好的幫助，所以這裏跟着文檔上的例子實現了IDictionary接口，實現了一個字典類型的基本功能。所以代碼寫在這裏，記錄一下自己的學習過程。

IDictionary接口的實現過程代碼如下：

using System;
using System.Linq;
using System.Reflection;
using System.Collections.Generic;
using System.Collections;

namespace 類型_Type
{
    /// <summary>
    /// This class implements a simple dictionary using an array of dictionary
    /// DictionaryEntry objects
    /// </summary>
    class SimpleDictionary :IDictionary
    {
        // The array of items
        public DictionaryEntry[] items;
        private Int32 ItemsInUse;

        // Construct the SimpleDictionary with desired number of items
        // The number of items can not change for the life time of this SimpleDictionary

        public SimpleDictionary(Int32 numItems)
        {
            items = new DictionaryEntry[numItems];
        }

        #region IDictionary Members

        public bool IsReadOnly { get { return false; } }
        public bool Contains(object key)
        {
            Int32 index;
            return TryGetIndexOfKey(key, out index);
        }
        public bool IsFixedSize { get { return false; } }
        public void Remove(object key)
        {
            if (key == null) throw new ArgumentNullException();
            // Try to find out the key in DictionaryEntry array
            Int32 index;
            if(TryGetIndexOfKey(key,out index))
            {
                // If key is found,slide all the items up
                Array.Copy(items, index + 1, items,index, ItemsInUse - index - 1);
                ItemsInUse--;
            }
            else
            {
                // If the key is not the dictionary just return;
                return;
            }
        }

        public void Clear() { ItemsInUse = 0; }
        public void Add(object key,object value)
        {
            // Add the new key/value pair even if this key already exists in the dictionary
            if(ItemsInUse==items.Length)
            {
                throw new InvalidCastException("The dictionary could not hold any more items");
            }
            else
            {
                items[ItemsInUse++] = new DictionaryEntry(key, value);
            }
        }

        public ICollection Keys
        {
            get
            {
                object[] keys = new object[ItemsInUse];
                for(Int32 i=0;i<ItemsInUse;i++)
                {
                    keys[i] = items[i].Key;
                }
                return keys;
            }
        }

        public ICollection Values
        {
            get
            {
                object[] values = new object[ItemsInUse];
                for(Int32 i=0;i<ItemsInUse;i++)
                {
                    values[i] = items[i].Value;
                }
                return values;
            }
        }

        public int Count { get { return ItemsInUse; } }

        public object SyncRoot { get { throw new NotImplementedException(); } }

        public bool IsSynchronized { get { return false; } }

        public object this[object key]
        {
            get
            {
                // If this key is in the dictionary then return its value
                Int32 index;
                if(TryGetIndexOfKey(key,out index))
                {
                    // The key was foun then return its value
                    return items[index].Value;
                }
                else
                {
                    // The key was not found then return null
                    return null;
                }
            }
            set
            {
                // If the key is in the dictionary then change its value
                Int32 index;
                if(TryGetIndexOfKey(key,out index))
                {
                    // The key was found then change its value
                    items[index].Value = value;
                }
                else
                {
                    // The key was not found then add this key/value pair
                    Add(key, value);
                }
            }
        }


        private bool TryGetIndexOfKey(object key, out int index)
        {
           for(index=0;index<ItemsInUse;index++)
            {
                 if(items[index].Key == key)
                {
                    return true;
                }
            }
            return false;
        }

        public IDictionaryEnumerator GetEnumerator()
        {
            // Construct and return an enumrator
            return new SimpleDictionaryEnumrator(this);
        }

        public void CopyTo(Array array, int index)
        {
            
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            // Construct and return an enumerator.
            return new SimpleDictionaryEnumrator(this);
        }
        #endregion

    }
    class SimpleDictionaryEnumrator : IDictionaryEnumerator
    {
        // A copy of the SimpleDictionary object's key/value
        public DictionaryEntry[] items;
        Int32 Index = -1;
        public SimpleDictionaryEnumrator(SimpleDictionary sp)
        {
            items = new DictionaryEntry[sp.Count];
            Array.Copy(sp.items, 0, items,0, sp.Count);
        }
        // Return the current items
        public object Current 
        {
            get
            { 
                ValidateIndex();
                return items[Index]; 
            } 
        }

        public object Key { get { ValidateIndex();return items[Index].Key; } }

        public object Value { get { ValidateIndex();return items[Index].Value; } }

        public DictionaryEntry Entry { get { return items[Index]; } }

        private void ValidateIndex()
        {
            if(Index<0 || Index>=items.Length)
            {
                throw new InvalidOperationException("Enumrator is before or after the collection");
            }
        }
        public bool MoveNext()
        {
            if(Index<items.Length-1)
            {
                Index++;
                return true;
            }
            return false;
        }

        public void Reset()
        {
            Index = -1;
        }
    }

    class Program
    {

        static void Main(string[] args)
        {
            // Create a dictionary that contains no more than three entries
            IDictionary d = new SimpleDictionary(5);
            d.Add("English", 70);
            d.Add("French", 80);
            d.Add("Math", 90);
            
            Console.WriteLine($"Number of elements in dictionary={d.Count}");
            Console.WriteLine($"Your English score is:{d["English"]}");// 按key來查詢

            //刪除一個存在的鍵值對
            d.Remove("Math");
            Console.WriteLine($"After remove,The Number of elements in dictionary={d.Count}");
            Console.WriteLine("字典d中的所有鍵爲如下：");
            // 遍歷
            foreach(string str in d.Keys)
            {
                Console.WriteLine(str);
            }

            //遍歷鍵值對
            Console.WriteLine("遍歷鍵值對");
            foreach(DictionaryEntry de in d)
            {
                Console.WriteLine($"鍵：{de.Key}\t值:{de.Value}");
            }
            Console.ReadKey();
        }
    }
}
// 代碼的運行結果如下：
//Number of elements in dictionary=3
//Your English score is:70
//After remove, The Number of elements in dictionary=2
//字典d中的所有鍵爲如下：
//English
//French
//遍歷鍵值對
//鍵：English 值:70
//鍵：French 值:80

參考文章