treeview menu

var parent = _context.DataTable.Where(x => x.ParentId == null).Select(x => x.Id).ToList();//Get all parent Node
List<yourclass> child = _context.DataTable.Include(x => x.ChildTable).ToList().Where(x => parentIcfStandardIds.Contains(x.Id)).ToList();
var Nodes = RecurseIcfRows(child);
TreeView1.Nodes.AddRange(Nodes);


private TreeNode[] RecurseIcfRows(List<yourclass> rows)
{
var nodeList = new List<TreeNode>();
//TreeNode node = null;
foreach (var dr in rows)
{
var parent = new TreeNode { Text = dr.Word + "(" + dr.Code + ")" };
long noteId = dr.Id;

parent.Name = noteId.ToString();
parent.ToolTipText = noteId.ToString();

if (nodeList.Find(FindNode) == null)
{
var childRows = dr.ChildStandards;
if (childRows.Count > 0)
{
// Recursively call this function for all childRowsl
TreeNode[] childNodes = RecurseIcfRows(childRows.ToList());

// Add all childnodes to this node.
parent.Nodes.AddRange(childNodes);
}

// Mark this noteID as dirty (already added).
//doneNotes.Add(noteID);
nodeList.Add(parent);
}
}

// Convert this List<TreeNode> to an array so it can be added to the parent node/TreeView.
TreeNode[] nodeArr = nodeList.ToArray();
return nodeArr;
}

This Work only when parentid and childid in same datatable
like
ID Parent ID Level Description
1 0 0 Root Node
2 1 1 First Child
3 1 1 Second Child
4 2 2 First Grand Child

Finally.......!

 protected void Page_Load(object sender, EventArgs e)
  {
  DropDownList1.DataSource = mydb.Recursives;
  DropDownList1.DataTextField = "Title";
  DropDownList1.DataValueField = "id";
  DropDownList1.DataBind();

  if (!IsPostBack)
  {
  var parentlist = mydb.Recursives.Where(p => p.ParentID == null).First();
  int? parId = 0;
  TreeNode firstParent = getTreeNode(parentlist, ref parId);
  TreeView1.Nodes.Add(firstParent);
  addnew(firstParent, parId);
  }
  }

  private void addnew(TreeNode firstParent, int? parId)
  {
  var childlist = mydb.Recursives.Where(p => p.ParentID == parId);
  foreach (Recursive item in childlist)
  {
  int? pId = 0;
  TreeNode tmp = getTreeNode(item, ref pId);
  firstParent.ChildNodes.Add(tmp);
  addnew(tmp , pId);
  }
  }
  private static TreeNode getTreeNode(Recursive parentlist, ref int? parid)
  {
  TreeNode firstParent = new TreeNode();
  firstParent.Text = parentlist.Title;
  firstParent.Value = "" + parentlist.id;
  parid = parentlist.id;
  return firstParent;
  }

Also look at this for ASP.NET Menu.
http://obout.com/em/em_whatis.aspx 

To determine what is parent, what is a child, your database has to support that. It has to store level of a Tree node. For example, level 0 will be the root level nodes, with an ID. First level of nodes will have level = 1 and a parent. So database table should have these columns in addition to what you already have.


ID   Parent ID    Level    Description 
1     0               0         Root Node
2     1               1         First Child
3     1               1         Second Child
4     2               2         First Grand Child


When you build your tree, first you will get all the nodes with Level 0 and create them as root level of children. Then you will build a recursive loop and find the first root level node, find all children with parent 0 and add them to that root node and so on.

 

Many thanks Mahesh Chand,
But I've already looked at these post and unfortunately wasn't that helpful.
I need to populate the tree view from the database using entity and I cant seems to get it right.
How do you determine which will be the child and which will be the parent?

The old post (i.e .net 2 ) speeks about node.ID which I cant seems to find.

Cheers

mk

Here are two more articles on ASP.NET TreeView.

TreeView control in asp.net 3.5

Display Directory Structure Using TreeView Control in ASP.NET

Here is a good link on ASP.NET TreeView.

ASP.NET TreeView

ASP.NET
Many thanks

ASP.NET or Windows Forms or WPF?