This article illustrates the use of C # indexed properties. Share it for your reference. The details are as follows:

This shows how the C # class declares indexed properties to represent array-like collections of different kinds of things.

// indexedproperty.cs
using System;
public class Document
{
  // 以下类型允许文档的查看方式与字的数组1样：
  public class WordCollection
  {
    readonly Document document; // 包含文档
    internal WordCollection(Document d)
    {
      document = d;
    }
    // Helper 函数 -- 从字符“begin”开始在字符数组“text”中搜索
    // 字数“wordCount”。如果字数小于 wordCount，
    // 则返回 false。将“start”和
    // “length”设置为单词在文本中的位置和长度:
    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;
    }
    // 获取和设置包含文档中的字的索引器：
    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))
        {
          // 用字符串“value”替换位于 start/length 处的
          // 字：
          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();
      }
    }
    // 获取包含文档中字的计数：
    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;
      }
    }
  }
  // 以下类型允许文档的查看方式像字符的“数组”
  // 1样：
  public class CharacterCollection
  {
    readonly Document document; // 包含文档
    internal CharacterCollection(Document d)
    {
     document = d;
    }
    // 获取和设置包含文档中的字符的索引器：
    public char this[int index]
    {
      get
      {
        return document.TextArray[index];
      }
      set
      {
        document.TextArray[index] = value;
      }
    }
    // 获取包含文档中字符的计数：
    public int Count
    {
      get
      {
        return document.TextArray.Length;
      }
    }
  }
  // 由于字段的类型具有索引器，
  // 因此这些字段显示为“索引属性”：
  public WordCollection Words;
  public CharacterCollection Characters;
  private char[] TextArray; // 文档的文本。
  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?"
    );
    // 将字“peter”更改为“penelope”：
    for (int i = 0; i < d.Words.Count; ++i)
    {
      if (d.Words[i] == "peter")
        d.Words[i] = "penelope";
    }
    // 将字符“p”更改为“P”
    for (int i = 0; i < d.Characters.Count; ++i)
    {
      if (d.Characters[i] == 'p')
        d.Characters[i] = 'P';
    }
    Console.WriteLine(d.Text);
  }
}

I hope this article is helpful to everyone’s C # programming.