Following is the table structure, and code for creating and filling the n level heirarchical treeview control using Recursion on your web (aspx) page, In my case I used the Component Art grid control, It can be any heirarchical control with Node property.
Here is an assumption that there is a TreeviewControl On your page.

Table Structure

[ID]             [Data]                              [ParentId]
101             Node1                              Null
102             Node2                              Null
103             Node1_Node1                   101
104             Node1_Node2                   101 
105             Node2_Node1                   102 
106             Node2_Node2                   102
107             Node2_Node1_Node1        102

Function
private void FillData(TreeViewNode parentNode)
{
   DataSet ds = new DataSet();SqlConnection cnn = new SqlConnection("Data Source=.\\sqlexpress;Initial Catalog=Testing;Integrated Security=True");
   SqlDataAdapter da;
   cnn.Open();
   if (parentNode==null)
      da = new SqlDataAdapter("Select [ID], [Data], [ParentId] from Treedata Where ParentId IS Null", cnn);
   else
      da = new SqlDataAdapter("Select [ID], [Data], [ParentId] from Treedata Where ParentId=" + parentNode.ID , cnn);
   da.Fill(ds);
   Response.Write(ds.Tables[0].Rows.Count);
   foreach (DataRow dataRow in ds.Tables[0].Rows)
   {
      ComponentArt.Web.UI.TreeViewNode node;
      node = new ComponentArt.Web.UI.TreeViewNode();
      node.ID = dataRow["ID"].ToString();
      node.Text = dataRow["Data"].ToString();
      if (parentNode==null)
      {
         TreeView1.Nodes.Add(node);
      }
      else 
      {
         parentNode.Nodes.Add(node); 
      }

         //Recursive call
         FillData(node);
   }

//Call the function with null argument
FillData(null);

I believe this will be the good one for you....enjoy