Create a treeview c# asp.net - expand all nodes

Question

I am having issues trying to build a treeview using asp.net and c#.

My outcome is trying to show a treeview like this (sorry for wrong spellings or wrong location but this is just test data):

UK 
   -> London
     -> SouthEast
        ->Kent
        ->Essex
     -> NorthEast
        ->Cambridge
Wales
   -> Cardiff

Here is my code below:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="WebApplication1.WebForm1"
    ValidateRequest="false" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <asp:TreeView ID="TreeView1" runat="server" >
                </asp:TreeView>
    </form>
</body>
</html>

C# :

using System;
using System.Collections.Generic;
using System.Web.UI.WebControls;
using System.Collections.ObjectModel;

namespace WebApplication1
{  
    public partial class WebForm1 : System.Web.UI.Page
    {
        public class ViewModel
        {           
            public string LocationName { get; set; }           
        }
        protected void Page_Load(object sender, EventArgs e)
        {
            ICollection<ViewModel> list = new Collection<ViewModel>();
            list.Add(new ViewModel { LocationName = "UK" });
            list.Add(new ViewModel { LocationName = "UK.London.SouthEast.Kent" });
            list.Add(new ViewModel { LocationName = "UK.London.SouthEast.Essex" });
            list.Add(new ViewModel { LocationName = "Wales.Cardiff" });
            list.Add(new ViewModel { LocationName = "Wales" });
            list.Add(new ViewModel { LocationName = "UK.London.NorthEast.Cambridge" });

            PopulateTreeview(list);
        }

        private void PopulateTreeview(ICollection<ViewModel> listOfCities)
        {
            foreach (ViewModel vm in listOfCities)
            {
                    TreeNode tnNode = new TreeNode();
                    tnNode.Text = vm.LocationName;
                    tnNode.Value = vm.LocationName;                    
                    tnNode.Expanded = true;                   
                    TreeView1.Nodes.Add(tnNode);                
            }
        }
    }
}

As you can see my test data is this format "UK.London.SouthEast.Essex". I will get this data from DB. I need to build a parent node and child nodes using this data but dont know how to? Been trying for few days to write how to do this.

Have you done a google search.. there are a lot of examples.. here is a StackOverFlow example of the same question do you understand linq or lambda's ?? http://stackoverflow.com/questions/447639/how-to-build-an-asp-net-treeview-from-scratch — MethodMan, Feb 20 '12 at 13:47
It's because you're doing it all wrong; you're adding all children to the root node without even *looking* at the hierarchy, so how do you expect it to work? — Shai, Feb 20 '12 at 13:47

score 2 · Answer 1 · answered Feb 20 '12 at 13:54

You are populating the TreeView as if it was a List. You will need to specify the hierarchy in order to populate the tree correctly...

Have a look at: http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.treenode.childnodes.aspx

Each node should be added with its respective children. You on the other hand specify that all the nodes should be placed under the "root".

Create a treeview c# asp.net - expand all nodes

1 Answers1