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Posted

So I have encountered a probleem while trying to populate a TreeView control with nodes. I hope that there are a some kind people who t

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Posted

What have you worked out so far? We need something to start at. :)

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Posted

        private static TreeView GetTree(TreeView Tree, List<string[]> Items)
        {
            foreach (string[] item in Items)
            {
                TreeNode parent = new TreeNode();
                parent.Text = item[0];
                TreeNode child = new TreeNode();
                child.Text = item[1];
                TreeNode child2 = new TreeNode();
                child2.Text = item[2];
                child.Nodes.Add(child2);
                parent.Nodes.Add(child);
                Tree.Nodes.Add(parent);
            }
            return Tree;
        }

Well, I have a code  that goes through each array and creates parentnode with array first item, childnode with second and childnode of childnode with third. So thats pretty basic approach

 

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Posted

I imagine you want to do something like the following pseudo code.
Idea is that you create the array of children you want before you create the treenode with the label.

tv = new TreeView();
dict = new Dictionary<String, List<String>>();
arrs = array of those arrays;

for arr in arrs:
     dict[arr[1]].Add(arr[2]);

for (key, value) in dict:
    tv.Nodes.Add(new TreeNode(key, value.ToArray()))
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Posted

 

I imagine you want to do something like the following pseudo code.
Idea is that you create the array of children you want before you create the treenode with the label.
 

 

Got lost trying to implement something like that, although the approach is right, I need to create the last level nodes first

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Posted

Got lost trying to implement something like that, although the approach is right, I need to create the last level nodes first

 If you provide the code you have, we can see what needs to be changed to fix it.

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Posted

What sort of performance are you looking for?  If you're just talking a few hundred items, then try this approach.

 

Each node should be identifiable via a predictable, unique key of your creation (it could be, literally, the value you're trying to insert).  Try to find your parent node by looking for the key it should have.  If you can't find it, create a new node and insert it.  If it returns something instead, then use that as the parent of the key you're trying to insert.

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Posted

Try a recursive function.

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Posted

Try a recursive function.

This is the right way to go, I know that, but I am totally unsure how the code should look like.

Regarding to performance, it is important in my case since we're talking about thousands of nodes here.

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Posted

This is the right way to go, I know that, but I am totally unsure how the code should look like.

Regarding to performance, it is important in my case since we're talking about thousands of nodes here.

 

As a general rule of thumb, if you find yourself pushing program state into some sort of explicit stack when using an iterative solution (pushing state to a queue for example): you are may just be doing an explicit recursion (what I mean by this is that you are doing the same work that a recursion would do for you) and are may be better suited to just use a recursive solution.

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Posted

This should be very straightforward to convert to C#, but here's the general idea for a recursive solution:

InitTreeView:
    var data = new List<string[]> { " Your data here " };
    foreach array in data:
        AddArray(array, 0, root collection)

AddArray(array, index, nodes):
    // Termination condition: index is past the end of the array
    // Otherwise:
    nextNode = AddValue(array[index], nodes)
    AddArray(array, index + 1, nextNode collection)

AddValue(value, nodes):
    // If node exists in the collection, return it
    // Otherwise create new node with the value, add it and return it

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Posted

 

This should be very straightforward to convert to C#, but here's the general idea for a recursive solution:


InitTreeView:
    var data = new List<string[]> { " Your data here " };
    foreach array in data:
        AddArray(array, 0, root collection)

AddArray(array, index, nodes):
    // Termination condition: index is past the end of the array
    // Otherwise:
    nextNode = AddValue(array[index], nodes)
    AddArray(array[index], index + 1, nextNode collection)

AddValue(value, nodes):
    // If node exists in the collection, return it
    // Otherwise create new node with the value, add it and return it

Some parts of the code still remain as a puzzle for me:
1)  What should AddValue return, a collection or a treenode?

2) AddArray( array[index].... seems weird to me, it expects an array, but your code sends it a value from array with that index

3) What should AddArray return? my best guess so far is, it is just a void and does not return anything.

4) nextNode collection should be nextNode.Nodes ? (case the AddValue returns a treenode)

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Posted

Some parts of the code still remain as a puzzle for me:

1)  What should AddValue return, a collection or a treenode?

2) AddArray( array[index].... seems weird to me, it expects an array, but your code sends it a value from array with that index

3) What should AddArray return? my best guess so far is, it is just a void and does not return anything.

4) nextNode collection should be nextNode.Nodes ? (case the AddValue returns a treenode)

1) As I wrote it, it returns a TreeNode. You could just return the collection as well as that's the only thing AddArray needs.

2) Oops that was a mistake, fixed. Should pass array.

3) AddArray is void.

4) Yup.

 

Is this homework?

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Posted

        private static TreeView GetTree(TreeView Tree)
        {
            Tree.BeginUpdate();
            List<string[]> l_tree = new List<string[]>();
            string[] str1 = new string[] {"Example", "2", "1"};
            string[] str2 = new string[] { "Example", "2", "2"};
            string[] str3 = new string[] { "Example", "3", "0" };
            l_tree.Add(str1);
            l_tree.Add(str2);
            l_tree.Add(str3);

            foreach (string[] array in l_tree)
            {
                AddArray(array, 0, Tree.Nodes);
            }
            Tree.EndUpdate();
            return Tree;
        }

        private static void AddArray(string[] array, int index, TreeNodeCollection nodes)
        {
            if (index < 3)
            {
                var nextNode = AddValue(array[index], nodes);
                AddArray(array, index + 1, nextNode.Nodes);
            }
        }

        private static TreeNode AddValue(string value, TreeNodeCollection nodes)
        {
            if (nodes.Count == 0)
            {
                TreeNode newnode = new TreeNode();
                newnode.Text = value;
                nodes.Add(newnode);
                return newnode;
            }
            else
            {
                foreach (TreeNode node in nodes)
                {
                    if (node.Text == value)
                    {
                        return node;
                    }
                    else
                    {
                        TreeNode newnode = new TreeNode();
                        newnode.Text = value;
                        node.Nodes.Add(newnode);
                        return node;
                    }
                }
            }
            return null;
        }

If the initial tree is empty, I get nullreferenceexception, since I cant go through the empty collection in addvalue

Example

 2

  1

    2

    0

  3

 

 

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Posted

Use IndexOfKey to find the item and set the Name property of the node when you create it so IndexOfKey can look for that.

 

Is this homework? If not I could just post a working example.

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Posted

No it is not a homework, its for my own Project. We at the computer science course are at the Python at the moment

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Posted

        void InitTreeView(List<string[]> arrays) {
            foreach (var array in arrays) {
                AddArray(array, 0, m_treeView.Nodes);
            }
        }


        /// <summary>
        /// Recursively adds each element of the array to the tree
        /// </summary>
        void AddArray(string[] array, int index, TreeNodeCollection nodes) {
            // Termination condition: we've past the bounds of the array
            if (index < array.Length) {
                var nextNode = AddValue(array[index], nodes);
                AddArray(array, index + 1, nextNode.Nodes);
            }
        }


        /// <summary>
        /// If the value exists, returns it, otherwise creates a new value
        /// </summary>
        TreeNode AddValue(string value, TreeNodeCollection nodes) {
            var index = nodes.IndexOfKey(value);
            if (index == -1) {
                var newNode = new TreeNode(value) { Name = value };
                nodes.Add(newNode);
                return newNode;
            }
            return nodes[index];
        }

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Posted

Sir I am truly thankful for your help, not sure how to return the regards :)

 

 

code

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Posted

Sir I am truly thankful for your help, not sure how to return the regards :)

Glad to be of help. :) By the way, you can write this:

    List<string[]> l_tree = new List<string[]>();
    string[] str1 = new string[] {"Example", "2", "1"};
    string[] str2 = new string[] { "Example", "2", "2"};
    string[] str3 = new string[] { "Example", "3", "0" };
    l_tree.Add(str1);
    l_tree.Add(str2);
    l_tree.Add(str3);

more simply as:

    var l_tree = new List<string[]> {
        new[] { "Example", "2", "1" },
        new[] { "Example", "2", "2" },
        new[] { "Example", "3", "0" }
    }

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Posted

I haven't tested but are you required to use the new[] syntax for the string arrays(i.e. string[]) in this example or can you get away with removing that part because of the string type?

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Posted

I haven't tested but are you required to use the new[] syntax for the string arrays(i.e. string[]) in this example or can you get away with removing that part because of the string type?

new[] { "a", "b" }

 is shorthand (since C# 3.0) for :

new string[] { "a", "b" }

There's also a special case (which was just to copy C/C++ in C# 1.0) for assignment to a new variable, where you can omit everything:

string[] array = { "a", "b" }

But then you have to explicitely type the variable, you can't use var. IMO this is old fashioned and for consistency everyone should write:

var array = new[] { "a", "b" }

Of course this works for all types and not just string.

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Posted

new[] { "a", "b" }

 is shorthand (since C# 3.0) for :

new string[] { "a", "b" }

There's also a special case (which was just to copy C/C++ in C# 1.0) for assignment to a new variable, where you can omit everything:

string[] array = { "a", "b" }

But then you have to explicitely type the variable, you can't use var. IMO this is old fashioned and for consistency everyone should write:

var array = new[] { "a", "b" }

Of course this works for all types and not just string.

 

 

Right, right, Is the special case for assignment still possible in newer C# revisions or is is not-recommended/depreciated? I initially thought that you were being a bit more verbose with the new[] statement in the compound list assignment because it was required. Sounds like you were doing it more for consistencies sake; which is fair.

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Posted

Right, right, Is the special case for assignment still possible in newer C# revisions or is is not-recommended/depreciated? I initially thought that you were being a bit more verbose with the new[] statement in the compound list assignment because it was required. Sounds like you were doing it more for consistencies sake; which is fair.

I'm doing it in the list assignment because it is and has always been required in that case. You can omit new[] only if you assign the array expression to an explicitely typed variable. This, in addition to the fact that this syntax contradicts the usual C# principle that every expression has a type, makes it inconsistent and confusing in my eyes, but it's still supported. It's only my opinion and not any sort of official deprecation or recommendation.

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Posted

I'm doing it in the list assignment because it is and has always been required in that case. You can omit new[] only if you assign the array expression to an explicitely typed variable. This, in addition to the fact that this syntax contradicts the usual C# principle that every expression has a type, makes it inconsistent and confusing in my eyes, but it's still supported. It's only my opinion and not any sort of official deprecation or recommendation.

 

Fair enough, I'll say that the bolded text is a good reason to use it in the above code regardless of opinion ;-)

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