Inheriting the Hashtable class

[mooman_fl]

I am trying to make a new class, IndexedHashtable. The idea is that each DictionaryEntry in the hashtable has an index number that you can search by as well as by the usual method (by key name). I can get it to do this rather easy with the following code:

 

Public Class IndexedHashtable
Inherits Hashtable
Public ReadOnly Property ItemByIndex(ByVal index As Integer) As DictionaryEntry
	Get
		Dim _index As Integer = Me.Count - 1
		Dim item As DictionaryEntry
		If index > (Me.Count - 1) Then Throw New IndexOutOfRangeException
		For Each item In Me
			If _index = index Then Return item
			_index += 1
		Next
	End Get
End Property
End Class

 

The problem is that if I add items to the hashtable then iterate through the index the index numbers don't return the entries in the order they were added. Almost, but not quite. As an example, made a form with a button and add the following code:

 

		Dim count As Integer
	Dim test As IndexedHashtable
	Dim dict As DictionaryEntry
	test = New IndexedHashtable
	test.Add("First", "Uno")
	test.Add("Second", "Dos")
	test.Add("Third", "Tres")
	test.Add("Fourth", "Quatro")
	test.Add("Fifth", "Sinco")
	test.Add("Sixth", "Seis")
	For count = 0 To (test.Count - 1)
		dict = test.ItemByIndex(count)
		Console.WriteLine("Key: {0} Value: {1}", dict.Key, dict.Value)
	Next

 

This produces the following output:

 

Key: Fourth Value: Quatro

Key: First Value: Uno

Key: Second Value: Dos

Key: Third Value: Tres

Key: Fifth Value: Sinco

Key: Sixth Value: Seis

Notice that index 0 is the fourth item that was added... everything else is in order. Is there a reason for this? Am I missing something? And most importantly is there a better, or more efficient way, of getting the results I am looking for?

[keitsi]

I've also noticed this behavior.

 

You could use arraylist to keep the order? I mean like adding the keys to arraylist in the order they were added, then

Return Me(arraylist(index))

 

That takes up a bit more memory though.

[Nerseus]

Use the SortedList class, no need to make your own.

 

-Nerseus

[mooman_fl]

Thank you Nersus... somehow I had missed that class. That is exactly what I was looking for.

[Rodenberg]

The point of a hashtable is to insert objects into an index derived by their hash value. This means that 2 objects, regardless of type or value, will not necessarily be inserted next to each other. Determining location is what the key is used for ;)

[mooman_fl]

The point of a hashtable is to insert objects into an index derived by their hash value. This means that 2 objects' date=' regardless of type or value, will not necessarily be inserted next to each other. Determining location is what the key is used for ;)[/quote']

I kind of got that impression from the way things worked.

 

Anyway I simply went with a SortedList since I needed the flexibility of both ways of doing things. So far I have no complaints.