/*
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);
}
}
}
}
Class Interface
Illustrates the use of an indexer
/*
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]);
}
}
Implements an indexer in a class
/*
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]);
}
}
}
illustrates the use of an indexer 1
/*
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();
}
}
}
}
Indexer: allow array like index
/*
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
Define indexer
/*
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
Create a specifiable range array class
/*
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("
");
// 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("
");
// 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("
");
}
}
[/csharp]