• Indexers enable objects to be indexed in a similar way to arrays.
• A get accessor returns a value. A set accessor assigns a value.
• The this keyword is used to define the indexers.
• The value keyword is used to define the value being assigned by the set indexer.
• Indexers do not have to be indexed by an integer value; it is up to you how to define the specific look-up mechanism.
• Indexers can be overloaded.
• Indexers can have more than one formal parameter, for example, when accessing a two-dimensional array.

• Indexers in C#, appears very similar to Property, with parameters.
• Can be used as arrays in Class or Struct
• Enables the objects to be sterilized and retrieved with an index.
• contains get ( that keeps tract of the index) and "set" handles the corresponding values. 
• Accessors
  • get accessors
    • return var_array[index];
  • set accessors
    • var_array[index]= value;

using System;
//csc indexers_concept_1.cs
//here <custome_index> is a Generics type.
namespace ex_indexer_1
{
class test_indexers<custom_index>
{
private custom_index[] arr = new custom_index[100];
public custom_index this[int i]
{
get
{
Console.WriteLine("get array Index : {0}", i);
return arr[i];
}
set
{
arr[i] = value;
Console.WriteLine("\tset value {0}",arr[i] = value);
} }
}

class test {
static void Main()
{
test_indexers<string> str = new test_indexers<string>();
test_indexers<string> str1 = new test_indexers<string>();
str[0] = "Hello, World";
System.Console.WriteLine(str[0]);
Console.ReadLine();
System.Console.WriteLine("---view like array--");
str1[0] = "Hello";
str1[1]= "world";
System.Console.WriteLine("{0}{1}{2}",str1[0],"-",str1[1]);
Console.ReadLine();
}
}
}