The Item property can be used to add or update values. The statement:
myHashtable.Item("abc") = sourceObject
either updates the value associated with the key "abc" (if it already exists in the hashtable) or adds it as a new item with the key "abc" (if it does not yet exist in the hashtable).
If key does not exist in the hashtable when you attempt to retrieve a value, the Item property returns Nothing.
To guard against inadvertently adding a member to the hashtable when you intend to modify an existing value, call the ContainsKey method to test the key.
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 DictionaryEntry object containing a single key/value pair.