programming-for-dummies

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Using a Collection
When you add data to a collection, you can optionally also assign a key to
that data, which you can later use to search and retrieve that data again. So
if you wanted to add the data Mike Ross along with the key moron, you
could use the following command:
HitList.Add (“Mike Ross”, “moron”)
When adding a key to data in a collection, your key must meet these criteria:
✦ You must add a key at the same time you add data to a collection.
After you add data to a collection, you can’t go back later and add a key
to that data.
✦ Every key must be a string.
✦ Every key must be unique; no two items in a collection can share the
same key.
Searching and retrieving data
After you store data in a collection, here are two ways to search and retrieve
data from that collection:
✦ Use the index number of that data.
✦ Use the key of that data.
If you don’t store a key with data originally, you can’t retrieve that data with
a key.
Index numbers
To retrieve data based on its location, you can do something as simple as
the following:
Dim Junk as New Collection
Junk.Add (3.1415)
Junk.Add (99)
Junk.Add (“Bo”)
If you wanted to retrieve the name Bo from the collection, you’d have to
know that Bo is stored as the third item (index number 3), so the following
would store the string Bo in the Good variable:
Good = Junk.Item(3)
The problem with relying on index numbers alone is that as you add and
delete items from a collection, the index numbers may change, as shown in
Figure 3-6.