将开发过程中常用的内容记录起来，下面的资料是关于C#索引属性使用范例的代码。

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using System;

public class Document
{
    public class WordCollection
    {

        internal WordCollection(Document d)
        {
           document = d;
        }

        private bool GetWord(char[] text, int begin, int wordCount, 
   out int start, out int length) 
        { 
            int end = text.Length;
            int count = 0;
            int inWord = -1;
            start = length = 0; 

            for (int i = begin; i <= end; ++i) 
            {
                bool isLetter = i < end && Char.IsLetterOrDigit(text[i]);

                if (inWord >= 0) 
                {
                    if (!isLetter) 
                    {
                        if (count++ == wordCount) 
                        {
                            start = inWord;
                            length = i - inWord;
                            return true;
                        }
                        inWord = -1;
                    }
                }
                else 
                {
                    if (isLetter)
                        inWord = i;
                }
            }
            return false;
        }

        public string this[int index] 
        {
            get 
            { 
                int start, length;
                if (GetWord(document.TextArray, 0, index, out start, 
                      out length))
                    return new string(document.TextArray, start, length);
                else
                    throw new IndexOutOfRangeException();
            }
            set 
            {
                int start, length;
                if (GetWord(document.TextArray, 0, index, out start, 
                     out length)) 
                {
                    if (length == value.Length) 
                    {
                        Array.Copy(value.ToCharArray(), 0, 
                                 document.TextArray, start, length);
                    }
                    else 
                    {
                        char[] newText = 
                            new char[document.TextArray.Length + 
       value.Length - length];
                        Array.Copy(document.TextArray, 0, newText, 
                    0, start);
                        Array.Copy(value.ToCharArray(), 0, newText, 
         start, value.Length);
                        Array.Copy(document.TextArray, start + length,
                                   newText, start + value.Length,
                                  document.TextArray.Length - start
                        - length);
                        document.TextArray = newText;
                    }
                }                    
                else
                    throw new IndexOutOfRangeException();
            }
        }

        public int Count 
        {
            get 
            { 
                int count = 0, start = 0, length = 0;
                while (GetWord(document.TextArray, start + length, 0, 
          out start, out length))
                    ++count;
                return count; 
            }
        }
    }

    public class CharacterCollection
    {

        internal CharacterCollection(Document d)
        {
          document = d; 
        }

        public char this[int index] 
        {
            get 
            { 
                return document.TextArray[index]; 
            }
            set 
            { 
                document.TextArray[index] = value; 
            }
        }

        public int Count 
        {
            get 
            { 
                return document.TextArray.Length; 
            }
        }
    }

    public WordCollection Words;
    public CharacterCollection Characters;

    public Document(string initialText)
    {
        TextArray = initialText.ToCharArray();
        Words = new WordCollection(this);
        Characters = new CharacterCollection(this);
    }

    public string Text 
    {
        get 
        { 
           return new string(TextArray); 
        }
    }
}

class Test
{
    static void Main()
    {
        Document d = new Document(
           "peter piper picked a peck of pickled peppers. How many pickled peppers did peter piper pick?"
        );

        for (int i = 0; i < d.Words.Count; ++i) 
        {
            if (d.Words[i] == "peter") 
                d.Words[i] = "penelope";
        }

        for (int i = 0; i < d.Characters.Count; ++i) 
        {
            if (d.Characters[i] == 'p')
                d.Characters[i] = 'P';
        }

        Console.WriteLine(d.Text);
    }
}