This sample shows how C# classes can declare indexed properties to represent an array-like collection of different kinds of things.
This sample contains the source code for the Indexed Properties Tutorial.
Building and Running the Sample Within Visual Studio
To build and run the Indexed Properties sample
1. Open the solution (IndexedProperties.sln).
2. From the Debug menu, click Start Without Debugging.
Building and Running the Sample from the Command Line
To build and run the Indexed Properties sample
* Type the following at the command prompt:
csc indexedproperty.cs
indexedproperty
// indexedproperty.cs
using System;
public class Document
{
// Type allowing the document to be viewed like an array of words:
public class WordCollection
{
readonly Document document; // The containing document
internal WordCollection(Document d)
{
document = d;
}
// Helper function -- search character array "text", starting at
// character "begin", for word number "wordCount." Returns false
// if there are less than wordCount words. Sets "start" and
// length" to the position and length of the word within text:
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;
}
// Indexer to get and set words of the containing document:
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))
{
// Replace the word at start/length with the
// string "value":
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();
}
}
// Get the count of words in the containing document:
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;
}
}
}
// Type allowing the document to be viewed like an "array"
// of characters:
public class CharacterCollection
{
readonly Document document; // The containing document
internal CharacterCollection(Document d)
{
document = d;
}
// Indexer to get and set characters in the containing document:
public char this[int index]
{
get
{
return document.TextArray[index];
}
set
{
document.TextArray[index] = value;
}
}
// Get the count of characters in the containing document:
public int Count
{
get
{
return document.TextArray.Length;
}
}
}
// Because the types of the fields have indexers,
// these fields appear as "indexed properties":
public WordCollection Words;
public CharacterCollection Characters;
private char[] TextArray; // The text of the document.
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?"
);
// Change word "peter" to "penelope":
for (int i = 0; i < d.Words.Count; ++i)
{
if (d.Words[i] == "peter")
d.Words[i] = "penelope";
}
// Change character "p" to "P"
for (int i = 0; i < d.Characters.Count; ++i)
{
if (d.Characters[i] == 'p')
d.Characters[i] = 'P';
}
Console.WriteLine(d.Text);
}
}
