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| c# indexer |
INDEXERS IN C#
“Indexer is a class member, which
gives access to a value of class just like array, and class behaves like virtual
array not like an original array.” It is used to provide access to the class’s
fields outside form the class like properties but that is another case.
SYNTAX
[<modifier>] <type> this [<parameter list>]
{
[get{statements}] //Get accessor
[set{statements}] // Set accessor
}
Syntax Explanation
- Here the modifier may be public
private or other.
- In type what type of value will
provide that may be string, int, decimal or double but the best type is object
because it return all the possible type int string double all.
- Where this pointing that we are
going to define a indexer on the current class in which we declaring indexer.
- And the last get and set block will include your logic of getting and setting
the values of class. Either you can permit to getting only or setting only but
you can permit the both like properties in c#.
- Parameter list may be parameter
type list which can be string type, double type, care type or int type etc. and
will write like this <int index> or <string name>, but what is the
difference between this means if you use int type the index parameter will be
number and if you use string type the indexing parameter will be some name on
behalf of name we can access the values to get and set. But there is problem with
name that is c# is case sensitive and conditioner is most of it if we make any
name case diff. to the original then the assignment does not success and return
any null name, this issue will be solved by convert the given name into either
upper case and check or convert into lower case and check see example to
understand.
We use ‘else
if’ construct to provide get and set accessor to the values which will clear in
example see below. According to the index number mean 0, 1, 2 or 1, 2, 3 the
values will be accessible to get and set.
c# Indexer examples
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| c# indexer examples |
EXAMPLES 1 (INDEX TROUGH INTEGER’S VALUES)
Suppose we have
student entity/class and some attributes/fields then we will make two class one
for main program and second for the declaring and initializing the values or attributes.
Let see
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Main class
namespace StudentIndexer
{
class Program
{
static void Main(string[] args)
{
StdAttributes std = new
StdAttributes(12, "Afreen", "8th", "dadar
campus", "Morning", 1200.00);
Console.WriteLine("Student Roll Number =" + std[1]);
Console.WriteLine("Student Name =" + std[2]);
Console.WriteLine("Student Class =" + std[3]);
Console.WriteLine("Student Campus Name =" + std[4]);
Console.WriteLine("Student Timing =" + std[5]);
Console.WriteLine("Student Fees =" + std[6]);
std[1] = 10; std[2] = "Arslan";
std[3] = "9th standard"; std[4] = "Malwarcampus"; std[5]
= "Evening"; std[6] = 1450.00;
Console.WriteLine();
Console.WriteLine("Modified Student
Roll Number =" + std[1]);
Console.WriteLine("Modified Student
Name =" + std[2]);
Console.WriteLine("Modified Student
Class =" + std[3]);
Console.WriteLine("Modified Student
Campus Name =" + std[4]);
Console.WriteLine("Modified Student
Timing =" + std[5]);
Console.WriteLine("Modified Student
Fees =" + std[6]);
Console.ReadKey();
}
}
}
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Attribute/fields class
namespace StudentIndexer
{
class StdAttributes
{
int Stdno;
string Stdname, Stdclass, Stdcampus,
Stdtiming;
double Stdfee;
public StdAttributes(int Stdno,string
Stdname,string Stdclass,string Stdcampus,string Stdtiming,double Stdfee)
{
this.Stdno = Stdno;
this.Stdname = Stdname;
this.Stdclass = Stdclass;
this.Stdcampus = Stdcampus;
this.Stdtiming = Stdtiming;
this.Stdfee = Stdfee;
}
public object this[int index]
{
get
{
if (index == 1)
return Stdno;
else if (index == 2)
return Stdname;
else if (index == 3)
return Stdclass;
else if (index == 4)
return
Stdcampus;
else if (index == 5)
return Stdtiming;
else if (index == 6)
return Stdfee;
return null;
}
set
{
if (index == 1)
Stdno =(int)value;
else if (index == 2)
Stdname = (string)value;
else if (index == 3)
Stdclass = (string)value;
else if (index == 4)
Stdcampus = (string)value;
else if (index == 5)
Stdtiming = (string)value;
else if (index == 6)
Stdfee = (double)value;
else;
}
}
}
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EXAMPLES (INDEX TROUGH STRING NAME)
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Main class
namespace StudentIndexer
{
class Program
{
static void Main(string[] args)
{
StdAttributes std = new
StdAttributes(12, "Afreen", "8th", "dadar
campus", "Morning", 1200.00);
Console.WriteLine("Student Roll Number =" + std["stdno"]);
Console.WriteLine("Student Name =" + std["stdname"]);
Console.WriteLine("Student Class =" + std["stdclass"]);
Console.WriteLine("Student Campus Name =" + std["Stdcampus"]);
Console.WriteLine("Student Timing =" + std["stdTiming"]);
Console.WriteLine("Student Fees =" + std["stdfee"]);
std["stdno"] = 10; std["stdname"]
= "Arslan"; std["stDclass"] = "9th standard";
std["stdcampus"] = "Malwarcampus"; std["stdtiming"]
= "Evening"; std["stdfee"] = 1450.00;
Console.WriteLine();
Console.WriteLine("Modified Student
Roll Number =" + std["stdno"]);
Console.WriteLine("Modified Student
Name =" + std["stdname"]);
Console.WriteLine("Modified Student
Class =" + std["stDclass"]);
Console.WriteLine("Modified Student
Campus Name =" + std["stdcampus"]);
Console.WriteLine("Modified Student
Timing =" + std["stdtiming"]);
Console.WriteLine("Modified Student
Fees =" + std["stdfee"]);
Console.ReadKey();
}
}
}
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Attributes/fields Class
namespace StudentIndexer
{
class StdAttributes
{
int Stdno;
string Stdname, Stdclass, Stdcampus,
Stdtiming;
double Stdfee;
public StdAttributes(int Stdno,string
Stdname,string Stdclass,string Stdcampus,string Stdtiming,double Stdfee)
{
this.Stdno = Stdno;
this.Stdname = Stdname;
this.Stdclass = Stdclass;
this.Stdcampus = Stdcampus;
this.Stdtiming = Stdtiming;
this.Stdfee = Stdfee;
}
public object this[string name]
{
get
{
if (name.ToLower()== "stdno")
return Stdno;
else if (name.ToLower() == "stdname")
return Stdname;
else if (name.ToLower() == "stdclass")
return Stdclass;
else if (name.ToLower() == "stdcampus")
return Stdcampus;
else if (name.ToLower() == "stdtiming")
return Stdtiming;
else if (name.ToLower() == "stdfee")
return Stdfee;
return null;
}
set
{
if (name.ToLower() == "stdno")
Stdno =(int)value;
else if (name.ToLower() == "stdname")
Stdname = (string)value;
else if (name.ToLower() == "stdclass")
Stdclass = (string)value;
else if (name.ToLower() == "stdcampus")
Stdcampus = (string)value;
else if (name.ToLower() == "stdtiming")
Stdtiming = (string)value;
else if (name.ToLower() == "stdfee")
Stdfee = (double)value;
else;
}
}
}
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