Csharp/C Sharp/Class Interface/Indexer
Содержание
- 1 A two-dimensional fail-soft array
- 2 C# Properties and Indexers
- 3 Create a specifiable range array class
- 4 Define indexer
- 5 Illustrates the use of an indexer
- 6 illustrates the use of an indexer 1
- 7 Implements an indexer and demonstrates that an indexer does not have to operate on an array
- 8 Implements an indexer in a class
- 9 indexed properties
- 10 Indexer: allow array like index
- 11 Indexers don"t have to operate on actual arrays
- 12 Indexer with complex logic
- 13 Indexing with an Integer Index
- 14 Indexing with an String Index
- 15 Indexing with Multiple Parameters
- 16 Overload the FailSoftArray indexer
- 17 Return class object from indexer
- 18 Two dimensional indexer
- 19 Use an indexer to create a fail-soft array
A two-dimensional fail-soft array
<source lang="csharp"> /* C#: The Complete Reference by Herbert Schildt Publisher: Osborne/McGraw-Hill (March 8, 2002) ISBN: 0072134852
- /
// A two-dimensional fail-soft array.
using System;
class FailSoftArray2D {
int[,] a; // reference to underlying 2D array
int rows, cols; // dimensions
public int Length; // Length is public
public bool errflag; // indicates outcome of last operation
// Construct array given its dimensions.
public FailSoftArray2D(int r, int c) {
rows = r;
cols = c;
a = new int[rows, cols];
Length = rows * cols;
}
// This is the indexer for FailSoftArray2D.
public int this[int index1, int index2] {
// This is the get accessor.
get {
if(ok(index1, index2)) {
errflag = false;
return a[index1, index2];
} else {
errflag = true;
return 0;
}
}
// This is the set accessor.
set {
if(ok(index1, index2)) {
a[index1, index2] = value;
errflag = false;
}
else errflag = true;
}
}
// Return true if indexes are within bounds.
private bool ok(int index1, int index2) {
if(index1 >= 0 & index1 < rows &
index2 >= 0 & index2 < cols)
return true;
return false;
}
}
// Demonstrate a 2D indexer. public class TwoDIndexerDemo {
public static void Main() {
FailSoftArray2D fs = new FailSoftArray2D(3, 5);
int x;
// show quiet failures
Console.WriteLine("Fail quietly.");
for(int i=0; i < 6; i++)
fs[i, i] = i*10;
for(int i=0; i < 6; i++) {
x = fs[i,i];
if(x != -1) Console.Write(x + " ");
}
Console.WriteLine();
// now, generate failures
Console.WriteLine("\nFail with error reports.");
for(int i=0; i < 6; i++) {
fs[i,i] = i*10;
if(fs.errflag)
Console.WriteLine("fs[" + i + ", " + i + "] out-of-bounds");
}
for(int i=0; i < 6; i++) {
x = fs[i,i];
if(!fs.errflag) Console.Write(x + " ");
else
Console.WriteLine("fs[" + i + ", " + i + "] out-of-bounds");
}
}
}
</source>
C# Properties and Indexers
<source lang="csharp"> using System; public PropertiesIndexers {
public static void Main()
{
Circle c = new Circle();
c.Radius = 35;
}
} class Circle {
public int Radius
{
get
{
return(radius);
}
set
{
radius = value;
Draw();
}
}
public void Draw()
{
}
int radius;
}
</source>
Create a specifiable range array class
<source lang="csharp"> /* C#: The Complete Reference by Herbert Schildt Publisher: Osborne/McGraw-Hill (March 8, 2002) ISBN: 0072134852
- /
/* Create a specifiable range array class.
The RangeArray class allows indexing to begin at some value other than zero. When you create a RangeArray, you specify the beginning and ending index. Negative indexes are also allowed. For example, you can create arrays that index from -5 to 5, 1 to 10, or 50 to 56.
- /
using System;
class RangeArray {
// private data
int[] a; // reference to underlying array
int lowerBound; // lowest index
int upperBound; // greatest index
// data for properties
int len; // underlying var for Length property
bool errflag; // underlying var for outcome
// Construct array given its size.
public RangeArray(int low, int high) {
high++;
if(high <= low) {
Console.WriteLine("Invalid Indices");
high = 1; // create a minimal array for safety
low = 0;
}
a = new int[high - low];
len = high - low;
lowerBound = low;
upperBound = --high;
}
// Read-only Length property.
public int Length {
get {
return len;
}
}
// Read-only Error property.
public bool Error {
get {
return errflag;
}
}
// This is the indexer for RangeArray.
public int this[int index] {
// This is the get accessor.
get {
if(ok(index)) {
errflag = false;
return a[index - lowerBound];
} else {
errflag = true;
return 0;
}
}
// This is the set accessor
set {
if(ok(index)) {
a[index - lowerBound] = value;
errflag = false;
}
else errflag = true;
}
}
// Return true if index is within bounds.
private bool ok(int index) {
if(index >= lowerBound & index <= upperBound) return true;
return false;
}
}
// Demonstrate the index-range array. public class RangeArrayDemo {
public static void Main() {
RangeArray ra = new RangeArray(-5, 5);
RangeArray ra2 = new RangeArray(1, 10);
RangeArray ra3 = new RangeArray(-20, -12);
// Demonstrate ra
Console.WriteLine("Length of ra: " + ra.Length);
for(int i = -5; i <= 5; i++)
ra[i] = i;
Console.Write("Contents of ra: ");
for(int i = -5; i <= 5; i++)
Console.Write(ra[i] + " ");
Console.WriteLine("\n");
// Demonstrate ra2
Console.WriteLine("Length of ra2: " + ra2.Length);
for(int i = 1; i <= 10; i++)
ra2[i] = i;
Console.Write("Contents of ra2: ");
for(int i = 1; i <= 10; i++)
Console.Write(ra2[i] + " ");
Console.WriteLine("\n");
// Demonstrate ra3
Console.WriteLine("Length of ra3: " + ra3.Length);
for(int i = -20; i <= -12; i++)
ra3[i] = i;
Console.Write("Contents of ra3: ");
for(int i = -20; i <= -12; i++)
Console.Write(ra3[i] + " ");
Console.WriteLine("\n");
}
}
</source>
Define indexer
<source lang="csharp"> /* Learning C# by Jesse Liberty Publisher: O"Reilly ISBN: 0596003765
- /
using System;
namespace Indexers
{
// a simplified ListBox control
class ListBoxTest
{
private string[] strings;
private int ctr = 0;
// initialize the listbox with strings
public ListBoxTest(params string[] initialStrings)
{
// allocate space for the strings
strings = new String[256];
// copy the strings passed in to the constructor
foreach (string s in initialStrings)
{
strings[ctr++] = s;
}
}
// add a single string to the end of the listbox
public void Add(string theString)
{
if (ctr >= strings.Length)
{
// handle bad index
}
else
strings[ctr++] = theString;
}
// allow array-like access
public string this[int index]
{
get
{
if (index < 0 || index >= strings.Length)
{
// handle bad index
}
return strings[index];
}
set
{
// add only through the add method
if (index >= ctr )
{
// handle error
}
else
strings[index] = value;
}
}
// publish how many strings you hold
public int GetNumEntries()
{
return ctr;
}
}
public class TesterListBoxTest
{
[STAThread]
static void Main()
{
// create a new listbox and initialize
ListBoxTest lbt =
new ListBoxTest("Hello", "World");
Console.WriteLine("After creation...");
for (int i = 0;i<lbt.GetNumEntries();i++)
{
Console.WriteLine("lbt[{0}]: {1}",i,lbt[i]);
}
// add a few strings
lbt.Add("Who");
lbt.Add("Is");
lbt.Add("John");
lbt.Add("Galt");
Console.WriteLine("\nAfter adding strings...");
for (int i = 0;i<lbt.GetNumEntries();i++)
{
Console.WriteLine("lbt[{0}]: {1}",i,lbt[i]);
}
// test the access
string subst = "Universe";
lbt[1] = subst;
// access all the strings
Console.WriteLine("\nAfter editing strings...");
for (int i = 0;i<lbt.GetNumEntries();i++)
{
Console.WriteLine("lbt[{0}]: {1}",i,lbt[i]);
}
}
}
}
</source>
Illustrates the use of an indexer
<source lang="csharp"> /* Mastering Visual C# .NET by Jason Price, Mike Gunderloy Publisher: Sybex; ISBN: 0782129110
- /
/*
Example10_11.cs illustrates the use of an indexer
- /
using System;
// declare the Car class class Car {
// declare two fields
private string make;
private string model;
// define a constructor
public Car(string make, string model)
{
this.make = make;
this.model = model;
}
// define the indexer
public string this[int index]
{
get
{
switch (index)
{
case 0:
return make;
case 1:
return model;
default:
throw new IndexOutOfRangeException();
}
}
/* set
{
switch (index)
{
case 0:
this.make = value;
break;
case 1:
this.model = value;
break;
default:
throw new IndexOutOfRangeException();
}
}*/
}
}
public class Example10_11 {
public static void Main()
{
// create a Car object
Car myCar = new Car("Toyota", "MR2");
// display myCar[0] and myCar[1]
Console.WriteLine("myCar[0] = " + myCar[0]);
Console.WriteLine("myCar[1] = " + myCar[1]);
// set myCar[0] to "Porsche" and myCar[1] to "Boxster"
Console.WriteLine("Setting myCar[0] to \"Porsche\" " +
"and myCar[1] to \"Boxster\"");
myCar[0] = "Porsche";
myCar[1] = "Boxster";
// myCar[2] = "Test"; // causes IndeXOutOfRangeException to be thrown
// display myCar[0] and myCar[1] again
Console.WriteLine("myCar[0] = " + myCar[0]);
Console.WriteLine("myCar[1] = " + myCar[1]);
}
}
</source>
illustrates the use of an indexer 1
<source lang="csharp"> /* Mastering Visual C# .NET by Jason Price, Mike Gunderloy Publisher: Sybex; ISBN: 0782129110
- /
/*
Example10_11.cs illustrates the use of an indexer
- /
using System;
public class Example10_11a {
public static void Main()
{
// create a Car object
Car myCar = new Car("Toyota", "MR2");
// display myCar[0] and myCar[1]
Console.WriteLine("myCar[0] = " + myCar[0]);
Console.WriteLine("myCar[1] = " + myCar[1]);
// set myCar[0] to "Porsche" and myCar[1] to "Boxster"
Console.WriteLine("Setting myCar[0] to \"Porsche\" " +
"and myCar[1] to \"Boxster\"");
myCar[0] = "Porsche";
myCar[1] = "Boxster";
// myCar[2] = "Test"; // causes IndeXOutOfRangeException to be thrown
// display myCar[0] and myCar[1] again
Console.WriteLine("myCar[0] = " + myCar[0]);
Console.WriteLine("myCar[1] = " + myCar[1]);
}
} // declare the Car class class Car {
// declare two fields
private string make;
private string model;
// define a constructor
public Car(string make, string model)
{
this.make = make;
this.model = model;
}
// define the indexer
public string this[int index]
{
get
{
switch (index)
{
case 0:
return make;
case 1:
return model;
default:
throw new IndexOutOfRangeException();
}
}
set
{
switch (index)
{
case 0:
this.make = value;
break;
case 1:
this.model = value;
break;
default:
throw new IndexOutOfRangeException();
}
}
}
}
</source>
Implements an indexer and demonstrates that an indexer does not have to operate on an array
<source lang="csharp"> /* C# Programming Tips & Techniques by Charles Wright, Kris Jamsa Publisher: Osborne/McGraw-Hill (December 28, 2001) ISBN: 0072193794
- /
// // Seedr.cs -- Implements an indexer and demonstrates that an indexer // does not have to operate on an array // // Compile this program with the following command line: // C:>csc Seed.cs // namespace nsIndexer {
using System;
public class Seedr
{
static public void Main ()
{
clsIndexed idx = new clsIndexed ();
Console.WriteLine ("The value is " + idx[900]);
}
}
class clsIndexed
{
public int this[int index]
{
get
{
DateTime now = DateTime.Now;
Random rand = new Random ((int) now.Millisecond);
return (rand.Next () % index);
}
}
}
}
</source>
Implements an indexer in a class
<source lang="csharp"> /* C# Programming Tips & Techniques by Charles Wright, Kris Jamsa Publisher: Osborne/McGraw-Hill (December 28, 2001) ISBN: 0072193794
- /
// // Indexer.cs -- Implements an indexer in a class // // Compile this program with the following command line: // C:>csc Indexer.cs // namespace nsIndexer {
using System;
public class Indexer
{
static public void Main ()
{
clsIndexed idx = new clsIndexed (10);
Console.WriteLine ("The value is " + idx[3]);
idx.Show (3);
}
}
class clsIndexed
{
public clsIndexed (int elements)
{
DateTime now = DateTime.Now;
Random rand = new Random ((int) now.Millisecond);
Arr = new int [elements];
for (int x = 0; x < Arr.Length; ++x)
Arr[x] = rand.Next() % 501;
}
int [] Arr;
public int this[int index]
{
get
{
if ((index < 0) || (index > Arr.Length))
throw (new ArgumentOutOfRangeException());
return (Arr[index]);
}
}
public void Show (int index)
{
Console.WriteLine ("The value is " + Arr[index]);
}
}
}
</source>
indexed properties
<source lang="csharp"> using System; public class Starter {
public static void Main() {
Names obj = new Names();
Console.WriteLine(obj[1]);
}
} public class Names {
object[,] _names ={{"V", 27},{"B", 35},{"D", 29}};
public object this[int index] {
get {
return _names[index, 0] + " " + _names[index, 1];
}
}
}
</source>
Indexer: allow array like index
<source lang="csharp"> /* Learning C# by Jesse Liberty Publisher: O"Reilly ISBN: 0596003765
- /
using System;
namespace Indexers
{
// a simplified ListBox control
public class ListBoxTest
{
private string[] strings;
private int ctr = 0;
// initialize the listbox with strings
public ListBoxTest(params string[] initialStrings)
{
// allocate space for the strings
strings = new String[256];
// copy the strings passed in to the constructor
foreach (string s in initialStrings)
{
strings[ctr++] = s;
}
}
// add a single string to the end of the listbox
public void Add(string theString)
{
strings[ctr] = theString;
ctr++;
}
// allow array-like access
public string this[int index]
{
get
{
if (index < 0 || index >= strings.Length)
{
// handle bad index
}
return strings[index];
}
set
{
strings[index] = value;
}
}
// helper method, given a string find
// first matching record that starts with the target
private int findString(string searchString)
{
for (int i = 0;i<strings.Length;i++)
{
if (strings[i].StartsWith(searchString))
{
return i;
}
}
return -1;
}
// index on string
public string this[string index]
{
get
{
if (index.Length == 0)
{
// handle bad index
}
return this[findString(index)];
}
set
{
strings[findString(index)] = value;
}
}
// publish how many strings you hold
public int GetNumEntries()
{
return ctr;
}
}
public class TesterIndexersList
{
public void Run()
{
// create a new listbox and initialize
ListBoxTest lbt =
new ListBoxTest("Hello", "World");
// add a few strings
lbt.Add("Who");
lbt.Add("Is");
lbt.Add("John");
lbt.Add("Galt");
// test the access
string subst = "Universe";
lbt[1] = subst;
lbt["Hel"] = "GoodBye";
// lbt["xyz"] = "oops";
// access all the strings
for (int i = 0; i<lbt.GetNumEntries(); i++)
{
Console.WriteLine("lbt[{0}]: {1}",i,lbt[i]);
}
}
[STAThread]
static void Main()
{
TesterIndexersList t = new TesterIndexersList();
t.Run();
}
}
}
</source>
Indexers don"t have to operate on actual arrays
<source lang="csharp"> /* C#: The Complete Reference by Herbert Schildt Publisher: Osborne/McGraw-Hill (March 8, 2002) ISBN: 0072134852
- /
// Indexers don"t have to operate on actual arrays.
using System;
class PwrOfTwo {
/* Access a logical array that contains
the powers of 2 from 0 to 15. */
public int this[int index] {
// Compute and return power of 2.
get {
if((index >= 0) && (index < 16)) return pwr(index);
else return -1;
}
// there is no set accessor
}
int pwr(int p) {
int result = 1;
for(int i=0; i<p; i++)
result *= 2;
return result;
}
}
public class UsePwrOfTwo {
public static void Main() {
PwrOfTwo pwr = new PwrOfTwo();
Console.Write("First 8 powers of 2: ");
for(int i=0; i < 8; i++)
Console.Write(pwr[i] + " ");
Console.WriteLine();
Console.Write("Here are some errors: ");
Console.Write(pwr[-1] + " " + pwr[17]);
Console.WriteLine();
}
}
</source>
Indexer with complex logic
<source lang="csharp"> using System; class MyValue {
private String[] Cards = new String[52];
public String this[int index] {
get {
return Cards[index];
}
set {
Cards[index] = value;
}
}
public String this[String CardName] {
get {
for (int i = 0; i < 52; i++) {
if (Cards[i] == CardName)
return Cards[i];
}
return Cards[0];
}
set {
for (int i = 0; i < 52; i++) {
if (Cards[i] == CardName)
Cards[i] = value;
}
}
}
public MyValue() {
int y = 0;
int i = 0;
while (i < 52) {
for (int x = 0; x < 13; x++) {
switch (y) {
case 0:
Cards[i] = (x + 1) + " A";
break;
case 1:
Cards[i] = (x + 1) + " B";
break;
case 2:
Cards[i] = (x + 1) + " C";
break;
case 3:
Cards[i] = (x + 1) + " D";
break;
}
if (y == 3)
y = 0;
else
y++;
i++;
}
}
}
} class MyValueClient {
public static void Main() {
MyValue PokerDeck = new MyValue();
String FourOfHearts = PokerDeck["4 of Hearts"];
Console.WriteLine(FourOfHearts);
}
}
</source>
Indexing with an Integer Index
<source lang="csharp"> /* A Programmer"s Introduction to C# (Second Edition) by Eric Gunnerson Publisher: Apress L.P. ISBN: 1-893115-62-3
- /
// 19 - Indexers and Enumerators\Indexing with an Integer Index // copyright 2000 Eric Gunnerson using System; using System.Collections; class DataValue {
public DataValue(string name, object data)
{
this.name = name;
this.data = data;
}
public string Name
{
get
{
return(name);
}
set
{
name = value;
}
}
public object Data
{
get
{
return(data);
}
set
{
data = value;
}
}
string name;
object data;
} class DataRow {
public DataRow()
{
row = new ArrayList();
}
public void Load()
{
/* load code here */
row.Add(new DataValue("Id", 5551212));
row.Add(new DataValue("Name", "Fred"));
row.Add(new DataValue("Salary", 2355.23m));
}
// the indexer
public DataValue this[int column]
{
get
{
return((DataValue) row[column - 1]);
}
set
{
row[column - 1] = value;
}
}
ArrayList row;
} public class IndexingwithanIntegerIndex {
public static void Main()
{
DataRow row = new DataRow();
row.Load();
Console.WriteLine("Column 0: {0}", row[1].Data);
row[1].Data = 12; // set the ID
}
}
</source>
Indexing with an String Index
<source lang="csharp"> /* A Programmer"s Introduction to C# (Second Edition) by Eric Gunnerson Publisher: Apress L.P. ISBN: 1-893115-62-3
- /
// 19 - Indexers and Enumerators\Indexing with an String Index // copyright 2000 Eric Gunnerson using System; using System.Collections; class DataValue {
public DataValue(string name, object data)
{
this.name = name;
this.data = data;
}
public string Name
{
get
{
return(name);
}
set
{
name = value;
}
}
public object Data
{
get
{
return(data);
}
set
{
data = value;
}
}
string name;
object data;
} class DataRow {
public DataRow()
{
row = new ArrayList();
}
public void Load()
{
/* load code here */
row.Add(new DataValue("Id", 5551212));
row.Add(new DataValue("Name", "Fred"));
row.Add(new DataValue("Salary", 2355.23m));
}
public DataValue this[int column]
{
get
{
return( (DataValue) row[column - 1]);
}
set
{
row[column - 1] = value;
}
}
int FindColumn(string name)
{
for (int index = 0; index < row.Count; index++)
{
DataValue dataValue = (DataValue) row[index];
if (dataValue.Name == name)
return(index);
}
return(-1);
}
public DataValue this[string name]
{
get
{
return( (DataValue) this[FindColumn(name)]);
}
set
{
this[FindColumn(name)] = value;
}
}
ArrayList row;
} public class IndexingwithanStringIndex {
public static void Main()
{
DataRow row = new DataRow();
row.Load();
DataValue val = row["Id"];
Console.WriteLine("Id: {0}", val.Data);
Console.WriteLine("Salary: {0}", row["Salary"].Data);
row["Name"].Data = "Barney"; // set the name
Console.WriteLine("Name: {0}", row["Name"].Data);
}
}
</source>
Indexing with Multiple Parameters
<source lang="csharp"> /* A Programmer"s Introduction to C# (Second Edition) by Eric Gunnerson Publisher: Apress L.P. ISBN: 1-893115-62-3
- /
// 19 - Indexers and Enumerators\Indexing with Multiple Parameters // copyright 2000 Eric Gunnerson using System; class Player {
string name;
public Player(string name)
{
this.name = name;
}
public override string ToString()
{
return(name);
}
} class Board {
Player[,] board = new Player[8, 8];
int RowToIndex(string row)
{
string temp = row.ToUpper();
return((int) temp[0] - (int) "A");
}
int PositionToColumn(string pos)
{
return(pos[1] - "0" - 1);
}
public Player this[string row, int column]
{
get
{
return(board[RowToIndex(row), column - 1]);
}
set
{
board[RowToIndex(row), column - 1] = value;
}
}
public Player this[string position]
{
get
{
return(board[RowToIndex(position),
PositionToColumn(position)]);
}
set
{
board[RowToIndex(position),
PositionToColumn(position)] = value;
}
}
} public class IndexingwithMultipleParameters {
public static void Main()
{
Board board = new Board();
board["A", 4] = new Player("White King");
board["H", 4] = new Player("Black King");
Console.WriteLine("A4 = {0}", board["A", 4]);
Console.WriteLine("H4 = {0}", board["H4"]);
}
}
</source>
Overload the FailSoftArray indexer
<source lang="csharp"> /* C#: The Complete Reference by Herbert Schildt Publisher: Osborne/McGraw-Hill (March 8, 2002) ISBN: 0072134852
- /
// Overload the FailSoftArray indexer.
using System;
class FailSoftArray {
int[] a; // reference to underlying array
public int Length; // Length is public
public bool errflag; // indicates outcome of last operation
// Construct array given its size.
public FailSoftArray(int size) {
a = new int[size];
Length = size;
}
// This is the int indexer for FailSoftArray.
public int this[int index] {
// This is the get accessor.
get {
if(ok(index)) {
errflag = false;
return a[index];
} else {
errflag = true;
return 0;
}
}
// This is the set accessor
set {
if(ok(index)) {
a[index] = value;
errflag = false;
}
else errflag = true;
}
}
/* This is another indexer for FailSoftArray.
This index takes a double argument. It then
rounds that argument to the nearest integer
index. */
public int this[double idx] {
// This is the get accessor.
get {
int index;
// round to nearest int
if( (idx - (int) idx) < 0.5) index = (int) idx;
else index = (int) idx + 1;
if(ok(index)) {
errflag = false;
return a[index];
} else {
errflag = true;
return 0;
}
}
// This is the set accessor
set {
int index;
// round to nearest int
if( (idx - (int) idx) < 0.5) index = (int) idx;
else index = (int) idx + 1;
if(ok(index)) {
a[index] = value;
errflag = false;
}
else errflag = true;
}
}
// Return true if index is within bounds.
private bool ok(int index) {
if(index >= 0 & index < Length) return true;
return false;
}
}
// Demonstrate the fail-soft array. public class FSDemo1 {
public static void Main() {
FailSoftArray fs = new FailSoftArray(5);
// put some values in fs
for(int i=0; i < fs.Length; i++)
fs[i] = i;
// now index with ints and doubles
Console.WriteLine("fs[1]: " + fs[1]);
Console.WriteLine("fs[2]: " + fs[2]);
Console.WriteLine("fs[1.1]: " + fs[1.1]);
Console.WriteLine("fs[1.6]: " + fs[1.6]);
}
}
</source>
Return class object from indexer
<source lang="csharp"> using System; public class MyValue {
public String Name;
} class CardDeck {
private MyValue[] Cards = new MyValue[52];
public MyValue this[int index] {
get {
return Cards[index];
}
set {
Cards[index] = value;
}
}
public static void Main(String[] args) {
try {
CardDeck PokerDeck = new CardDeck();
MyValue HiddenAce = PokerDeck[53];
} catch (IndexOutOfRangeException e) {
Console.WriteLine(e.Message);
} finally {
// Cleanup code
}
}
}
</source>
Two dimensional indexer
<source lang="csharp"> using System; class MultiplicationTable {
private int[,] MultiplicationArray = new int[10, 10];
public int this[int x, int y] {
get {
return MultiplicationArray[x, y];
}
set {
MultiplicationArray[x, y] = value;
}
}
public MultiplicationTable() {
for (int i = 0; i < 10; i++) {
for (int y = 0; y < 10; y++) {
MultiplicationArray[i, y] = i * y;
}
}
}
} class MultiplicationTableClient {
public static void Main(String[] args) {
MultiplicationTable MyTable = new MultiplicationTable();
Console.Write("3 x 9 is " + MyTable[3, 9]);
}
}
</source>
Use an indexer to create a fail-soft array
<source lang="csharp"> /* C#: The Complete Reference by Herbert Schildt Publisher: Osborne/McGraw-Hill (March 8, 2002) ISBN: 0072134852
- /
// Use an indexer to create a fail-soft array.
using System;
class FailSoftArray {
int[] a; // reference to underlying array
public int Length; // Length is public
public bool errflag; // indicates outcome of last operation
// Construct array given its size.
public FailSoftArray(int size) {
a = new int[size];
Length = size;
}
// This is the indexer for FailSoftArray.
public int this[int index] {
// This is the get accessor.
get {
if(ok(index)) {
errflag = false;
return a[index];
} else {
errflag = true;
return 0;
}
}
// This is the set accessor
set {
if(ok(index)) {
a[index] = value;
errflag = false;
}
else errflag = true;
}
}
// Return true if index is within bounds.
private bool ok(int index) {
if(index >= 0 & index < Length) return true;
return false;
}
}
// Demonstrate the fail-soft array. public class FSDemo {
public static void Main() {
FailSoftArray fs = new FailSoftArray(5);
int x;
// show quiet failures
Console.WriteLine("Fail quietly.");
for(int i=0; i < (fs.Length * 2); i++)
fs[i] = i*10;
for(int i=0; i < (fs.Length * 2); i++) {
x = fs[i];
if(x != -1) Console.Write(x + " ");
}
Console.WriteLine();
// now, generate failures
Console.WriteLine("\nFail with error reports.");
for(int i=0; i < (fs.Length * 2); i++) {
fs[i] = i*10;
if(fs.errflag)
Console.WriteLine("fs[" + i + "] out-of-bounds");
}
for(int i=0; i < (fs.Length * 2); i++) {
x = fs[i];
if(!fs.errflag) Console.Write(x + " ");
else
Console.WriteLine("fs[" + i + "] out-of-bounds");
}
}
}
</source>
