VB.NET Language in a Nutshell, Second Edition

Name

Hashtable.Item Property

Class

System.Collections.Hashtable

Syntax

                  hashtablevariable.Item(key)

hashtablevariable (required; Hashtable object)

A reference to a Hashtable object

key (required; Object)

The key whose value is to be retrieved

Return Value

An Object representing the value associated with key

Description

Returns an Object that is the value associated with a particular key/value pair.

Rules at a Glance

• Item is the default property of the Hashtable object, and since it is parameterized, we can write:

                          hashtablevariable(key)

• Item is a read/write property. In other words, you can use the Item property to retrieve the value belonging to a particular key, as well as to modify the value belonging to a particular key.

• If key does not exist in the hash table when you attempt to retrieve a value, the Item property returns Nothing.

• If key does not exist in the hash table when you attempt to modify a value, the key and its associated value are added to the hash table, as a sort of implicit add. For example, if the key "AK" does not exist in a hash table, the code fragment:

  hshStates.Item("AK") = "Alaska"

  adds the key "AK" and its associated value, "Alaska".

Programming Tips and Gotchas

• To guard against inadvertently adding a member to the hash table when you intend to modify an existing value, call the ContainsKey method beforehand.

• You can also retrieve individual members of the Hashtable object by iterating it using the For Each...Next statement. Each iteration of the loop returns a ...