Concept of Indexer in C#

This blog is useful to understand the concept of Class of Indexer in C#

Concept of Indexer

Indexer allow/enables an object to access the member of that class using an index notation.

1. Indexer exits only in C#.
2. If we want to use our object as an array we need to create indexer in our class.
             or
   If we want to use member variable our class to be indexed like an array for that object, this can be done by indexer.
3. Use for security purpose so that no one can access our private variable.
4. It contain two accessors set & get.

Syntax

this [Parameter]
{
    get
    {
        // Get codes goes here
    }
    set
    {
        // Set codes goes here
    }
} 

Properties of Indexer

1. Indexer increase usability.
2. Indexer may be abstract.
3. Indexer modifier can be private, public, protected or internal.
4. Indexer are uniquely identified by their parameters.
5. Indexer support inheritance.
6. The return type can be any valid C# types.
7. Indexers in C# must have at least one parameter. Else the compiler will generate a compilation error.
8. Outsider can't access & see that member of our class. In this case we are doing operator overloading of ( [ ] )subscripts.

Program

using System;
namespace IndexerExample
{
    class IndexExEmp
    {
        string name;
        string contact_no;
        string add;
        public string this[string Data]
        {
            get
            {
                switch (Data)
                {
                    case "Name": return name;
                    case "Contact_no": return contact_no;
                    case "Address": return add;
                    default: return "wrong property name";
                }
            }
            set
            {
                switch (Data)
                {
                    case "Name": name = value; break;
                    case "Contact_no": contact_no = value; break;
                    case "Address": add = value; break;
                }
            }
        }
        public string this[int i]
        {
            get
            {
                switch (i)
                {
                    case 1: return name;
                    case 2: return contact_no;
                    case 3: return add;
                    default: return "wrong index";
                }
            }
            set
            {
                switch (i)
                {
                    case 1: name = value; break;
                    case 2: contact_no = value; break;
                    case 3: add = value; break;
                }
            }
        }
        public static void Main(string[] aa)
        {
            IndexExEmp e = new IndexExEmp();
            e[1] = "Deepak dwij";
            e["add"] = "Govindpuram";
            e[2] = "9555918764";
            Console.WriteLine("the out put is looks like\n e[1] : {0}, e[2] : {1} & e[\"add\"] : {2} ", e[1], e[2], e["add"]);
            Console.ReadLine();
        }
    }
}

Output

Disadvantage

Indexers are slower than arrays.