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Creating TreeView from SQL database question

Posted on 2005-04-16
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Last Modified: 2010-04-16
I have a tree view and I want to display customer info that is stored in a database.   I would like to have nodes A through Z in the tree view, and when a user clicks to expand the letter it wll show all of the customers (the custname column) that start wit that letter.  Any ideas on how to accomplish this?
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Question by:ike2010
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caner_elci earned 1000 total points
ID: 13799412
There is no information about loading style of customers. I mean, do you want them to be loaded dynamically when the user expands a letter, or will they be loaded once in a startup method?

Anyway, I assume that you'll want to load them dynamically, because customer count may be more than thousands. You can do this to load your customers:

* I assume that there is a global TreeNode named parentNode which has all letter nodes as its children.
* Also, you'll need to add a dummy TreeNode to each letter node. Just to make them have a plus sign before them, so the user can expand the node.
* Add BeforeExpand event to your TreeView.
* You'll notice that there is a Node property in event arguments of this event.
* Write a code like this in the event handler:

      if( e.Node.Parent == parentNode && e.Node.Nodes.Count == 0 )
      {
            LoadCustomers(e.Node);
      }

* Write a dynamic loader:

      public void LoadCustomers(TreeNode node)
      {
            string firstLetter = node.Text;
            string sql = "select * from customers where customer_name like '"+firstLetter+"%'";

            node.Nodes.Clear();  // Clear dummy node here

            // execute sql here
            // fetch all rows and create a TreeNode for them, add each customer TreeNode to node.Nodes

            // if there are no rows selected starting with this letter, you'll decide to add a
            // dummy node again to allow user to retry loading customers later (recommended when your
            // application is a multiuser database application), otherwise, you may leave the node this way,
            // without any plus sign before it (without any children), meaning that there are no customers
            // starting with this letter and there will never be.
      }

I think it gives you an idea.

Caner ELCI
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