Concept of Indexers in C#

Prepared By : Uday Shah - HOD (IT)
Contact No : 7600044051

Indexers allow instances of a class or struct to be indexed just like arrays. Indexers resemble properties except that their accessors take parameters.

In the following example, a generic class is defined and provided with simple get and set accessor methods as a means of assigning and retrieving values. The Program class creates an instance of this class for storing strings.

class SampleCollection<T>
{
    // Declare an array to store the data elements. 
    private T[] arr = new T[100];

    // Define the indexer, which will allow client code 
    // to use [] notation on the class instance itself. 
    // (See line 2 of code in Main below.)         
    public T this[int i]
    {
        get
        {
            // This indexer is very simple, and just returns or sets 
            // the corresponding element from the internal array. 
            return arr[i];
        }
        set
        {
            arr[i] = value;
        }
    }
}

// This class shows how client code uses the indexer. 
class Program
{
    static void Main(string[] args)
    {
        // Declare an instance of the SampleCollection type.
        SampleCollection<string> stringCollection = new SampleCollection<string>();

        // Use [] notation on the type.
        stringCollection[0] = "Hello, World";
        System.Console.WriteLine(stringCollection[0]);
    }
}
// Output: 
// Hello, World.