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Understanding Indexer Methods

As programmers, we are very familiar with the process of accessing individual items contained

within a standard array using the index operator ([]), for example:

static void Main(string[] args)

{

// Loop over incoming start up params.

for(int i = 0; i < args.Length; i++)

Console.WriteLine("Args: {0}", args[i]);

// Declare an array of local integers.

int[] myInts = { 10, 9, 100, 432, 9874};

// Use the [] operator to access each element.

for(int j = 0; j < myInts.Length; j++)

Console.WriteLine("Index {0}  = {1} ", j,  myInts[j]);

Console.ReadLine();

}

The previous code is by no means a major newsflash. However, the C# language provides the

capability to design custom classes and structures that may be indexed just like a standard array, by

defining an indexer method. This particular language feature is most useful when you are creating

custom collection types (generic or nongeneric).

Before examining how to create such a construct, let’s begin by seeing one in action. Assume

you have added support for an indexer method to the custom PeopleCollection type developed in

Chapter 10 (specifically, the CustomNonGenericCollection project). Observe the following usage

within a new Console Application named SimpleIndexer:

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