Multiple Indexers In a Class Using Interface Indexers

Introduction

We all know about class indexers. Well, you can also have indexers in interfaces.

Interface indexers differ from class indexers in the following ways:

• Interface accessors do not use modifiers.
• An interface accessor does not have a body.
• The purpose of the accessor is to indicate whether the indexer is read-write, read-only, or write-only.

The following is an example of an interface indexer:

1. Open a new console project.
2. Create two interfaces, i.e., Interface1 and Interface2 (as shown below in the code).
3. Implement the indexer in each of the interfaces as shown below.
4. Create a class called as MyClass (as shown below) which implements these two interfaces.

Code:

class MyClass:Interface1,Interface2
{
  private int[] ArrayofStrings=new int[100];
  public MyClass()
  {
   
  }
 
  public int this[int index] /* Interface1 */
  {
   get
   {
    return ArrayofStrings[index];
   }
   set
   {
    ArrayofStrings[index]=value;
   }
  }
  
  string Interface2.this[int index]
  {
   get
   {
    return ArrayofStrings[index].ToString() + " String";
   }   
  }
}
 
public class MainClass
{
  public static void Main()
  {
   MyClass o = new MyClass();

   o[1] = 1; // interface1

   Console.WriteLine(((Interface2)o)[1].ToString());
   // Interface2

   Console.ReadLine();
  }
}
 
 
public interface Interface1
{
  int this[int index]
  {
   get;
   set;
  }       
}

public interface Interface2
{
  string this[int index]
  {
   get;
  }
}

You will notice that this class has two indexers, one coming from the Interface1 and other coming from Interface2. Indexer function for Interface1 has the access modifier as public whilst the indexer for Interface2 is private. Since the access modifier for indexer of Inferface1 is public, you can access it directly from the main as you would have accessed any other class indexer.

But you will notice that along with indexer for Interface1, you can also access the indexer for Interface2 by type casting, because the Interface2 is public.

Hence, in this way, you can have multiple indexers in a class using interface indexers.