How the generate TreeView in asp.net?_问答_开发者

Consider the following table. It has 3 filed with the following data. Now I want to show the data in TreeView Control in asp.net and c# I will select all the data in a DataTable.

category_id category_name   parents_id
1           Root            NUL开发者_如何学CL
2           Teacher         1
3           Student         1
4           TeacherA        2
5           TeacherB        2
6           TeacherC        2
7           StudentA        3
8           StudentB        3
9           StudentC        3

Here are some useful tips for you: for implementing tree view using asp.net and c#

NOte: I did not implement and did not use your datatable data here ....

TreeView control expects a heirarchical data structure, so we cant bind the DataTable to menu directly.
Use data table Select where ParentID = ID
Please use a recursive method to create child items relevent to current menu item ID

Here is an working example that you may use to transfer your ralational data structure (TABLE) to hierarchical data structure (TREE) using the relationship between ParentID and ID

<%@ Page Language="C#" %>
<html xmlns="http://www.w3.org/1999/xhtml">
 <head id="Head1" runat="server">
   <script runat="server">

protected override void OnLoad(EventArgs e)
{
    base.OnLoad(e);
    if (!this.IsPostBack)
        this.AddNodes(this.trvCategories.Nodes, 0, this.LoadData());
}
private void AddNodes(TreeNodeCollection nodes, int level, System.Data.DataTable dt)
{
    string filterExp = string.Format("ParentID='{0}'", level);
    foreach (System.Data.DataRow r in dt.Select(filterExp))
    {
        TreeNode item = new TreeNode()
        {
            Text = r[1].ToString(),
            Value = r[2].ToString()
        };
        this.AddNodes(item.ChildNodes, int.Parse(r[0].ToString()), dt);
        nodes.Add(item);
    }
}
private System.Data.DataTable LoadData()
{
    ///
    /// For the simplicity I do build the datatable dynamically,
    /// But you may get this data from the DATABASE
    ///
    System.Data.DataTable dt = new System.Data.DataTable();
    dt.Columns.Add("ID", String.Empty.GetType());
    dt.Columns.Add("[Name]", String.Empty.GetType());
    dt.Columns.Add("[Value]", String.Empty.GetType());
    dt.Columns.Add("ParentID", String.Empty.GetType());
    dt.Columns.Add("[Order]", String.Empty.GetType());
    int index = 9;
    for (int i = 0; i < 1100; i++)
    {
        string item = "{0},Item{1},Value{1},{2},{1}";
        if (i < 110)
        {
            index = i < 10 ? 0 : int.Parse(Math.Ceiling((decimal)i / 10).ToString());
            dt.Rows.Add((string.Format(item, i + 1, i, index)).Split(char.Parse(",")));
        }
        else
        {
            if (i % 10 == 0) index++;
            dt.Rows.Add((string.Format(item, i + 1, i, index)).Split(char.Parse(",")));
        }
    }
    return dt;
}

I recently posted some code on Code Review which answers this question. Here it is below, slightly modified for your table. I have tried to meet your needs by using a DataTable as the input, but I haven't used DataTables with LINQ before so you may need to edit slightly.

public TreeNode GenerateCategoriesTree(DataTable dt) {
  var s = new Stack<TreeNodeAndId>();
  var categories = dt.AsEnumerable();
  var rootCategory = categories.Single(o => o.Field<int?>("parents_id") == null);
  var rootNode = new TreeNode(rootCategory["category_name"].ToString(), rootCategory["category_id"].ToString());
  s.Push(new TreeNodeAndId { Id = Convert.ToInt32(rootCategory["category_id"]), TreeNode = rootNode });
  while (s.Count > 0) {
    var node = s.Peek();
    var current = categories.FirstOrDefault(o => o.Field<int?>("parents_id") == node.Id);
    if (current == null) {
      s.Pop();
      continue;
    }
    var child = new TreeNode(current["category_name"].ToString(), current["category_id"].ToString());
    node.TreeNode.ChildNodes.Add(child);
    s.Push(new TreeNodeAndId { Id = Convert.ToInt32(current["category_id"]), TreeNode = child });
    categories.Remove(current);
  }
  return rootNode;
}

struct TreeNodeAndId
{
  public TreeNode TreeNode;
  public int? Id;
}

If this doesn't build then at least I hope it will point you in the right direction.