Collections

arun_babu_a · November 9th, 2011, 03:25 AM

In the topic "Defining Collections"
we cant do-------

Code:

animalCollection[0].Feed();

can someone explain it little more and also the indexers and use of 'this' in this part.
Ch11 Page 285 and286

ChristianNagel · November 9th, 2011, 11:33 AM

animalCollection[0] returns the first element in the collection by using an indexer. animalCollection[0].Feed() invokes the Feed method on the first element of the collection.
The book on page 285 states this:

Quote:

You can't, however, do the following:
animalCollection[0].Feed();
To access items via their indices in this way, you need to use an indexer.

animalCollection is of type Animals and so far an indexer is not defined. On page 286 an indexer is defined.

Code:

public Animal this[int animalIndex]
{
   get
   {
      return (Animal)List[animalIndex];
   }
   set
   {
      List[animalIndex] = value;
   }
}

To explain "this" in this context, the book states this - I'm just changing the order of the sentence:
The indexer looks much like any other property. The difference to properties is that the this keyword is used along with parameters in square brackets.

Hope this helps.