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c# IDictionary接口的應用

本文转载自  xiaolei1982  查看原文  2008-03-31  0    c#/ 接口/ dictionary/ dict/ 应用           
using System;
using System.Collections.Generic;
using System.Collections;
using System.Text;

namespace fanxing
{

    public class SimpleDictionary : IDictionary
    {
        private DictionaryEntry[] items;
        private Int32 ItemsInUse = 0;

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

        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("key");
            Int32 index;
            if (TryGetIndexOfKey(key, out index))
            {
                Array.Copy(items, index + 1, items, index, ItemsInUse - index - 1);
                ItemsInUse--;
            }
            else
            {

            }
        }
        public void Clear()
        {
            if(ItemsInUse!=0)
            {
                for (int i = 0; i < ItemsInUse;i++ )
                {
                    items[i].Key = null;
                    items[9].Value = null;
                }
            }
            ItemsInUse = 0; 
        }
        public void Add(object key, object value)
        {
            try
            {
                if (ItemsInUse == items.Length)
                    throw new InvalidOperationException("The dictionary cannot hold any more items.");
                items[ItemsInUse++] = new DictionaryEntry(key, value);
            }
            catch (Exception e)
            {
                Console.Write(e.Message);
            }
        }
        public ICollection Keys
        {
            get
            {
                Object[] keys = new Object[ItemsInUse];
                for (Int32 n = 0; n < ItemsInUse; n++)
                    keys[n] = items[n].Key;
                return keys;
            }
        }
        public ICollection Values
        {
            get
            {
                Object[] values = new Object[ItemsInUse];
                for (Int32 n = 0; n < ItemsInUse; n++)
                    values[n] = items[n].Value;
                return values;
            }
        }
        public object this[object key]
        {
            get
            {
                Int32 index;
                if (TryGetIndexOfKey(key, out index))
                {
                    return items[index].Value;
                }
                else
                {
                    return null;
                }
            }

            set
            {
                Int32 index;
                if (TryGetIndexOfKey(key, out index))
                {
                    items[index].Value = value;
                }
                else
                {
                    Add(key, value);
                }
            }
        }
        private Boolean TryGetIndexOfKey(Object key, out Int32 index)
        {
            for (index = 0; index < ItemsInUse; index++)
            {
                if (items[index].Key.Equals(key)) return true;
            }
            return false;
        }
        private class SimpleDictionaryEnumerator : IDictionaryEnumerator
        {
            DictionaryEntry[] items;
            Int32 index = -1;

            public SimpleDictionaryEnumerator(SimpleDictionary sd)
            {
                items = new DictionaryEntry[sd.Count];
                Array.Copy(sd.items, 0, items, 0, sd.Count);
            }

            public Object Current { get { ValidateIndex(); return items[index]; } }

            public DictionaryEntry Entry
            {
                get { return (DictionaryEntry)Current; }
            }

            public Object Key { get { ValidateIndex(); return items[index].Key; } }

            public Object Value { get { ValidateIndex(); return items[index].Value; } }

            public Boolean MoveNext()
            {
                if (index < items.Length - 1) { index++; return true; }
                return false;
            }

            private void ValidateIndex()
            {
                if (index < 0 || index >= items.Length)
                    throw new InvalidOperationException("Enumerator is before or after the collection.");
            }

            public void Reset()
            {
                index = -1;
            }
        }
        public IDictionaryEnumerator GetEnumerator()
        {
            return new SimpleDictionaryEnumerator(this);//這里需要注意，返回的是一個接口，那我們new的類即SimpleDictionaryEnumerator就必須要繼承該接口，從而返回的該對象new SimpleDictionaryEnumerator(this)實例只能用IDictionaryEnumerator 接口下定義的方法。
        }

        public bool IsSynchronized { get { return false; } }
        public object SyncRoot { get { throw new NotImplementedException(); } }
        public int Count { get { return ItemsInUse; } }
        public void CopyTo(Array array, int index) { throw new NotImplementedException(); }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return ((IDictionary)this).GetEnumerator();
        }

       class Application7
       {

          static void Main(string[] args)
           {
               SimpleDictionary aa = new SimpleDictionary(2);
               aa.Add("a", "aaa");
               aa.Add("b", "aaa");
               Console.Write(aa.Keys.Count+"===="+aa.Values.Count);
               IEnumerable bb = aa;
               bb.GetEnumerator();
              foreach(DictionaryEntry cc in aa)
              {
                 Console.Write(cc.Key);
              }
               Console.Read();
           }
       }
    }
}
 
這是我抄自msdn的例子：
IDictionary接口是hashtable實現的重要接口，對於復雜的hashtable大家可能感覺過於麻煩，東西太多，一頭霧水，因為hashtable里面有許多東西實現起來卻是麻煩，許多數據結構的知識在里面，容易讓人郁悶。但是看了 SimpleDictionary 這個類的實現，大家就可以對hashtable的實現有了大體甚至是全局的了解，看了以后會讓你
茅塞頓開的，里面有些小細節與微軟的方法還是有出入，實現一個方法有很多種，只要實現即可。

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