How To Access Child Node / Collection Items In A Class Ways of accessing the child nodes of a Tree Node

[turbopowerdmaxsteel 0]

			Dim A As New TreeNode			MsgBox(A.Nodes(15).Text)			MsgBox(A.Nodes("WTF").Text)

Here are two ways of accessing the child nodes of a Tree Node, in this case, node A.

In the first case, we have accessed the child node with Index = 15 of node A.

In the second case, we have accessed the child node "WTF" by its key.

 

I want to be able to access the members of the Responses class in a similar fashion. Example:-

 

		MsgBox(Responses("ASL").Text)

Anybody knows how to go about creating the class?

 

What the... I missed out on the subject of the Topic..

 

Notice from Mark420:

I fixed the Topic title and Description for you

[faulty.lee 0]

			Dim A As New TreeNode			MsgBox(A.Nodes(15).Text)			MsgBox(A.Nodes("WTF").Text)

		MsgBox(Responses("ASL").Text)

I don't quite see the connection between the 2. Do you mean that you want to access the Responses as a Nodes? Are you referring to VB or ASP? It seems more like ASP to me. I think you need to give us more information regarding what you're trying to achieve.

[turbopowerdmaxsteel 0]

Its in VB .NET. I used the Node just an example, the same thing can be done using the Items collection of the ListView class. The idea is to create a collection of the class Responses and be able to access the individual items by using "key as String" instead of the regular way of doing "Index as Integer".Plainly speaking, we can access the individual elements of an array via the index number. How do we access the elements by a string "key" as we can in PHP. I don't think its possible to do the same for arrays in VB .NET, but doing that for a class is certainly. The TreeNode and the ListViewItem classes can be seen exhibiting this property.

[faulty.lee 0]

Its in VB .NET. I used the Node just an example, the same thing can be done using the Items collection of the ListView class. The idea is to create a collection of the class Responses and be able to access the individual items by using "key as String" instead of the regular way of doing "Index as Integer".
Plainly speaking, we can access the individual elements of an array via the index number. How do we access the elements by a string "key" as we can in PHP. I don't think its possible to do the same for arrays in VB .NET, but doing that for a class is certainly. The TreeNode and the ListViewItem classes can be seen exhibiting this property.

You can use Microsoft.VisualBasic.Collection. It has a built in key access for it's item. If you need to implement into your own class then you can try this

Public Class Responses	Private _responses As Microsoft.VisualBasic.Collection	Public Sub New()		Me._responses = New Microsoft.VisualBasic.Collection	End Sub	Default Public ReadOnly Property Item(ByVal Key As String) As String		' You can define the default type for this property		' Only readonly as per default of Collection.Item		Get			'You need to cast it if you have turn on Strict Mode			Return CType(Me._responses(Key), String)		End Get	End Property	' This is to ease the adding function	' In case you have a different type you want to store	Public Sub Add(ByVal Value As String, ByVal Key As String)		Me._responses.Add(Value, Key)	End SubEnd Class

to use it

		Dim a As Responses = New Responses		a.Add("testing", "key1")		MsgBox(a("key1"))

You can add as many member function as you like to customize or overrides the original base function. I didn't override the Add function exactly, but you should override all of "Add" if you want to implement any one of it, that way is to avoid confusion or improperly accessing the incorrect base function.

[miCRoSCoPiC^eaRthLinG 0]

You can definitely use the Microsoft.VisualBasic.Collection class as faulty.lee showed you - but a more elegant approach would be to create a separate class (inherited from CollectionBase) to hold your items and then use this class inside your Responses class.

 

For example - say I create a class called ResponsesCollection:

Imports System.CollectionsPublic Class ResponsesCollection	Inherits CollectionBaseEnd Class

CollectionBase provides you with an inbuilt searchable & sortable collection called List which can be accessed by both keys and index number. Any class inheriting CollectionBase gains these properties... The members methods which can operate on the List are Add, AddRange, Remove, RemoveAt, Clear, IndexOf, Item, Contains etc. Once you inherit a class from CollectionBase, you don't need to declare the List separately... you can directly access it as List.

 

A simple implementation of the members would be...

 Imports System.Collections  Public Class ResponsesCollection	 Inherits CollectionBase		Public Sub Add ( value As Object )					List.Add ( value )		End Sub		' AddRange		Public Sub AddRange( value[] As Object )					' Add items			ForEach vItem As Object in value				Add( vItem )		End Sub		' Remove		Public Sub Remove( value As Object )					' Remove item			List.Remove( value )		End Sub		' RemoveAt		Public Sub RemoveAt( index As Integer )					' If index is out of bounds - throw exception			If index > Count - 1 Or index < 0				Throw New ArgumentOutOfRangeException( "Index out of bounds." )			' If all is fine, remove item at specified index			List.RemoveAt( index )		End Sub		' Clear		Public Sub Clear()			' Clear List			List.Clear()		End Sub		' IndexOf		Public Function IndexOf( value As Object ) As Integer					Return List.IndexOf( value );		End Function		' Item		Public Function Item( index As Integer ) As Object			' If index is out of bounds - throw exception			If index > Count - 1 Or index < 0				Throw New ArgumentOutOfRangeException( "Index out of bounds." )			Return CType( List(index), Object)					End Function		' Insert		Public Sub Insert( index As Integer, value As Object )			List.Insert( index, value )		End Sub		' Contains		Public Function Contains( value As Object ) As Boolean			Return List.Contains( value );		End Function End Class

Once you're done with the collection class as shown above, go over to your Responses class and implement this class by a familiar object name (say Item) inside it... make sure you instantiate it in the constructor.

Public Class Responses	Public Item As ResponsesCollection	........	...........	' Constructor	Public Sub New	' Other constructor code	......	' Instantiate Collection	Item = New ResponsesCollection	....	End SubEnd Class

From now on whenever you instantiate Responses class anywhere in code, you'll be able to access/modify the list by Responses.Item (x) or Responses.Item.Add (x) or Responses.Item.RemoveAt (x) etc....

 

Let me know if this helped

 

Cheers,

m^e

[faulty.lee 0]

You can definitely use the Microsoft.VisualBasic.Collection class as faulty.lee showed you - but a more elegant approach would be to create a separate class (inherited from CollectionBase) to hold your items and then use this class inside your Responses class.

 

Hi miCRoSCoPiC^eaRthLinG,

 

I do agree with you, in fact i tries to avoid the VisualBasic namespace as much as possible. But looking at the situation, i think visualbasic.collection is much suited to get started. Maybe after turbopowerdmaxsteel got used to it, then he can try the actual more powerful collectionbase class.

 

turbopowerdmaxsteel, one thing to take note though, the starting index is different for visualbasic.collection and the collectionbase class. Visual basic one started with 1, for backward compatibility, where as collectionbase or system.collections starting with 0, similar to array

 

EDIT :

You can also inherits the visualbasic.collection. my last comment

You can add as many member function as you like to customize or overrides the original base function. I didn't override the Add function exactly, but you should override all of "Add" if you want to implement any one of it, that way is to avoid confusion or improperly accessing the incorrect base function.

 

actually referring to inheritance. Sorry for the mistake

 

Regards

faulty

Edited January 5, 2007 by faulty.lee (see edit history)

[turbopowerdmaxsteel 0]

Woah, that's a lot of detail. Thanx for the help, guys. It'll take a while to get accustomed to all these. I'll start off with the Microsoft.VisualBasic.Collection implementation.

Edited January 5, 2007 by turbopowerdmaxsteel (see edit history)