How do I create tree view for the following table using treeview control in C#

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it's coming from a table

l1 l2 l3
b bb bbh
b bb bbc
b bc bba

i want the treeview to be something like this

b
---bb
------bbh
------bbc
---bc
------bba

What I have tried:

I am new to c# kindly help and please let me know an easy way to implement it.

Posted 31-Jul-17 0:32am

Sourabh V Savanur

Updated 31-Jul-17 0:47am

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Comments

BillWoodruff 31-Jul-17 8:26am

Is this WinForm ? The complexity of the solution will depend on the extent to which the DataTable has a regular, invariant, structure.

Graeme_Grant 31-Jul-17 8:28am

Your guess is as good as mine

BillWoodruff 31-Jul-17 9:24am

I'm clear that I won't write code unless the context is clear.

"I do not enlighten those who are not eager to learn,
nor arouse those who are not anxious
to give an explanation themselves.
If I have presented one corner of the square
and they cannot come back to me with the other three,
I should not go over the points again."

From the "Analects" by Kong Fuzi (Confucius), approximately 2,500 years ago

:)

Graeme_Grant 31-Jul-17 10:00am

TreeViews are pretty much all the same ... so it took no effort ... but I do understand where you are coming from.

BillWoodruff 31-Jul-17 22:07pm

"TreeViews are pretty much all the same ..." I disagree: the WinForm TreeView has no equivalent to many WebUI features like 'PopulateOnDemand.'

Graeme_Grant 31-Jul-17 23:33pm

In the way that they work with Hierarchical data they are the same, each platform has their nuances as you point out.

You are right, not all platforms have "Populate on demand", WPF is another. But with a little creativity, it is not that hard to emulate. WinForms, for example, could be implemented something like this:

private void Form1_Load(object sender, EventArgs e)
{
    // initialise the tree here
    var nodeSomething = treeView1.Nodes.Add("Something");
    nodeSomething.Nodes.Add("Something below something");

    treeView1.AfterExpand += AfterExpand;
}

private void AfterExpand(object sender, TreeViewEventArgs e)
{
    foreach (TreeNode node in e.Node.Nodes)
    {
        // skip if we have already loaded data for this node
        if (node.Tag != null) 
            continue;
        node.Tag = new object();
        node.Nodes.AddRange(GetDataForThisNode(node));
    }
}

BillWoodruff 1-Aug-17 0:40am

I do admire your prolific coding ! What you've shown here is a kind of sketch/model for on-demand loading, which is great, but has nothing to do with the OP's concerns ... whatever they are.

The OP has (we hope) a DataTable: we don't know if that DataTable makes use of 'ChildRows, etc.; we don't know if the OP knows about DataBinding. We don't know if the OP has any idea what he really NEEDS to know :)

My goal is to get the OP to clarify what they are doing.

Graeme_Grant 1-Aug-17 0:47am

Yes, the OP's post was a bit vague, so I threw out a bit of code in hope of opening further dialogue.

The code above was only addressing your comment about "Populate on demand". And yes, I did open myself for those comments. :)

Graeme_Grant 1-Aug-17 0:50am

Any chance that you can clarify exactly what you need? More specific information will help in giving a more specific response.

Please click on the "Improve question" link to update with more specific information. If you are unsure of how to do this, the following link will explain how: FAQ - How to Improve your question[^]

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Graeme_Grant · Answer 1 · 2017-07-31T00:47:00

The TreeView control is a hierarchical data control. Child nodes need a reference to a parent node. So you should have a table that has the fields: Id & parentId. The child <> parent relationship is then parentId = Id

So once you load your data into a DataTable, you can do something like this:

C#

foreach (DataRow row in data.Rows)
{
    TreeNode node = new TreeNode(dr["field1"], dr["fieldId"])
    node.PopulateOnDemand = true;

     TreeView1.Nodes.Add(node);
 }
 
 protected void PopulateNode(Object sender, TreeNodeEventArgs e)
 {
     string fieldId = e.Node.Value;
     //select from table where parentId = fieldId.
     foreach (DataRow row in topics.Rows)
     {
         TreeNode node = new TreeNode(dr["field1"], dr["fieldId"])
         node.PopulateOnDemand = true;

         e.Node.ChildNodes.Add(node);
     }

 }