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Hi!
FOr the fun, I try to understand the recursivity in VB.net and I try to recreate a custom TreeView/TreeNode.
I progressively recreated the properties and methods of originals TreeView and TreeNode.
So, I have a customTreeView Class inheriting from Panel(for drawing with GDi), a customTreeNode class inheriting from Control and a customTreeNodeCollection inheriting from List(Of customTreeNode).
All customTreeNode instances and my instance of customTreeView have an instance of customTreeNodeCollection for storing childNodes.
I can add node the same way I do with originals TreeView ... with Add. But with the original, just after adding the childNodes to a parent node, if i check the "Level" property, it is already filled.
I don't understand, how, in my instance of customTreeNodeCollection, I can inform the Level of my New TreeNode.
I have to think well of recovering the level of the parent node and of adding +1 to it, but I does not manage either to recover parent TreeNode of the instance of this TreeNodeCollection.
Is there a trick know with recursivity ? or is there an other way to achieve it ?
Sorry for bad english 
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You do not tell it what level it is, all you do is set what the parent node is.
Look at the properties available, and the methods available on a tree node.
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The level / depth of the current node compared to the node root ... or, the number of parents.
"Look at the properties available, and the methods available on a tree node."
Yes, it would be easy using the true TreeNode, but it is not my case, I start from scratch for my TreeNode while inheriting Control.
So my question is:
I have nested list of nested list of nested lists ......
I'm on a node, how-to get his parent node and therefore, his level
And I think I must attribute this level in the "Add" method of my customTreeNodeCollection class. But I don't know, from this class, how-to access the instance of customTreeNode who have instanciated this collection 
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Look at Directory Recursion functions used for file systems, and apply the same principles to the nodes. i.e. have a function that can be called, pass in the current node, and keep a static count somewhere and keep walking up the parent until it is empty, then you will have the top (root node). and the depth to the node under test.
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Hi,
Maybe there is no need to store the level, just calculate the value when it's needed by walking up the list of nodes via the Parent property. The root or top node has no parent and the Parent property will return null or Nothing when you get there.
The first example using a loop is probably easier to understand than the second recursive version.
public Int32 Level() {
Int32 levelValue = 0;
Node node = this;
while (node.Parent != null) {
levelValue = levelValue + 1;
node = node.Parent;
}
return levelValue;
}
public Int32 Level() {
if (this.Parent == null) {
return 0;
} else {
return Level() + 1;
}
}
Sorry about using c# in the Basic forum. If you can't decipher it, post back and I'll attempt a translation.
Alan.
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I have searched in "Directory" for coll functions, but I don't know if it can serve me for my need.
Hi Alan N. As I sayed at start of this post, My first idea is to not using the real TreeNode and it's cool feature "Parent".
Since I want to write my own class inheriting "Control", I need to write my own property "Parent" because for controls, "Parent" is the parent control, and not the parent node.
I understand recursives functions for itering the child nodes (or child customTreeNodes in my List for my case), but I don't know how to make the same for going up in the parents.
I don't find simple examples on the web who make the same.
In any case, thank you for your suggestions which help me to consider the things in various ways.
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Hi,
Yes, I understood that you would be implementing your own version of the parent property which is different from the Control.Parent property and I think I see what the problem is. You are able to travel down through the tree via the node collections but from your description I would guess that there are no upward links in place. That is, if you pick any node in your tree you could go down to find it's children but not up to it's parent.
To be able to go both up and down each node must contain two links
CLASS Node
NodeCollection children
NodeCollection parent
and importantly the NodeCollection must contain a link to it's parent node
CLASS NodeCollection
Node parent
The overall data structure is an example of a Doubly Linked List, complicated by the fact that the elements of the list are alternating Nodes and NodeCollections.
Alan.
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Yes That's it. You have explained my problem better than me.
I succeeded in doing about what I wanted.
In the "Add" method of my customTreeNodeCollection, I call a recursive function which looks at all the children (and nested children) and informs their properties “Level” and “ParentNode”.
So, when I add a root node to the custom collection of my custom TreeView, this function can inform all the nodes 
My custom TreeNodeCollection
Public Class cTreeNodeCollection
Inherits List(Of cNode)
Public Overloads Sub Add(ByVal node As cNode)
MyBase.Add(node)
SetAllLevelsAndParents(node.ChildNodes, 1, node)
End Sub
Private Sub SetAllLevelsAndParents(ByVal nodeList As List(Of cNode), ByVal level As Int32, ByVal parentNode As cNode)
For Each n As cNode In nodeList
Console.WriteLine(level & " | " & n.Text)
n.Level = level
n.ParentNode = parentNode
SetAllLevelsAndParents(n.ChildNodes, level + 1, n)
Next
End Sub
End Class
But your help will be very helpfull !
The answer for me, is to pass in parameters the current node and it's level for the recursive function.
With the level+1, i can inform the level of the childs, and with the node, I can inform the parent of the childs.
I don't know if it's a robust solution, but it seems working for the moment.
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I am making an MCQ based quiz in VB 2008. I would like to have such an environment that picks up questions / answer options from a database (MS ACCESS) file and displays it to the user one after another. Say the quiz contains 20 questions.
How can this be done?
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Write some code to do it?
Try searching Google, MSDN or this site - you'll find plenty of info.
Regards
David R
---------------------------------------------------------------
"Every program eventually becomes rococo, and then rubble." - Alan Perlis
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Razanust wrote: displays it to the user one after another
Normally MCQ based quiz are not in sequence they are Random.
Razanust wrote: How can this be done?
at what stage are you. what is the difficulty / Problem you are having
SOFTDEV
If you have knowledge, let others light their candles at it. [ Let's work to help developers, not make them feel stupid ]
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I am a beginner to it.
Well the problem i am facing is that i can't find a proper procedure of how to link the questions with the help of databases to the VB Form.
That is if i want the label's text to be same as the variable say 'Question1' i would write text.label1= Question1
Now i want this thing to do with Access Database Files.
Any reference Article or sample code would be quite helpful.
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There are lots of good articles here on CodeProject. Maybe this[^] will interest you.
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I suggest you also have a look here[^].
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Thanks to all for your help.
I found another good video at http://vimeo.com/8618838.
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Hi all,
I'm using the unrar.dll and the decompressor-class.
I use a rar-file for extraction with:
Dim d As New Decompressor("filename")
d.UnPackAll("path")
After extraction I wan't to delete the rar-file by code, but I get
the message that the file is allready in use.
I can't find a process in task manager which I can delete.
And there is not event like "d.Dispose()" or "d.Close", "d = Nothing" didn't help too.
How can I set the file free for deleting?
Thanks all for help
br Maik
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The process that's holding the file open is most likely your own. Apparently, that library holds the file open for the life of the Decompressor object. Your best source of information would be the people who wrote that library.
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you could look at the documentation, and/or use Reflector, to discover some method that closes the input file; it might be called Close(). If all else fails, look for a Dispose() method.
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In VB6, it seems that the max height of a PictureBox or any other control is 245745.
Is there any way to extend the height of the PictureBox?
Thanks,
Bob
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Nope. You'd have to create you own from scratch.
The bigger question is why would you be displaying an image that large since there's no display in the world capable of showing it all?
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Maybe he is trying to rotate this[^] sideways?
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Do you know how I could develop my own? all I need is a container for other controls. Is ther an API that would let me build a container of any height I need?
Bob
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I don't know myself since I haven't touched VB6 in the last 9 years (even since I got my hands on the (VB.NET/.NET 1.0 Beta back around '01).
In VB.NET, it's a piece of cake. You cannot use VB.NET examples to do it in VB6 since VB6 doesn't support OOP nor the classes found in the .NET Framework.
And in the email that you sent me (I normally don't anwer them), the solution is not to make such a huge control. You don't need one that size. You just need to render on screen what is visible at the time.
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could someone help me change the sound card (if installed more than one) using winmm.dll?
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