Populate a TreeView from database
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
namespace treeTest
{
public partial class Form1 : Form
{
private List<Category> items = new List<Category>();
public Form1()
{
InitializeComponent();
}
/*
* dataSet1 has a table with 3 columns
* col#1=ID (int)
* col#2=ParentID (int)
* col#3=NodeText (string)
*/
private void Form1_Load(object sender, EventArgs e)
{
// Load up a dataset with values – usually from a database, but
// here I can show the data without using a real database.
dataSet1.Tables[0].Rows.Add(1, 0, “First Node”);
dataSet1.Tables[0].Rows.Add(3, 1, “Node 3.1″);
dataSet1.Tables[0].Rows.Add(4, 1, “Node 4.1″);
dataSet1.Tables[0].Rows.Add(5, 0, “Node 5.0″);
dataSet1.Tables[0].Rows.Add(6, 5, “Node 6.5″);
dataSet1.Tables[0].Rows.Add(7, 5, “Node 7.5″);
dataSet1.Tables[0].Rows.Add(8, 5, “Node 8.5″);
dataSet1.Tables[0].Rows.Add(9, 5, “Node 9.5″);
dataSet1.Tables[0].Rows.Add(10, 6, “Node 10.6″);
dataSet1.Tables[0].Rows.Add(11, 6, “Node 11.6″);
dataSet1.Tables[0].Rows.Add(12, 11, “Node 12.11″);
dataSet1.Tables[0].Rows.Add(13, 11, “Node 13.11″);
dataSet1.Tables[0].Rows.Add(14, 11, “Node 14.11″);
dataSet1.Tables[0].Rows.Add(15, 11, “Node 15.11″);
// Populate the items array of Catagory from the dataset
foreach (DataRow dr in dataSet1.Tables[0].Rows)
items.Add(new Category((int)dr[0], (int)dr[1], (string)dr[2]));
// Build the treeview from the catagory list
buildtree();
}
private void buildtree()
{
treeView1.Nodes.Clear(); // Clear any existing items
treeView1.BeginUpdate(); // prevent overhead and flicker
LoadBaseNodes(); // load all the lowest tree nodes
treeView1.EndUpdate(); // re-enable the tree
treeView1.Refresh(); // refresh the treeview display
}
private void LoadBaseNodes()
{
int baseParent = 0; // Find the lowest root category parent value
TreeNode node;
foreach (Category cat in items)
{
if (cat.ParentID < baseParent)
baseParent = cat.ParentID;
}
foreach (Category cat in items) // iterate through the categories
{
if (cat.ParentID == baseParent) // found a matching root item
{
node = treeView1.Nodes.Add(cat.NodeText); // add it to the tree
node.Tag = cat; // send the category into the tag for future processing
getChildren(node); // load all the children of this node
}
}
}
// recursive tree loader. Passes back in a node to retireve its childre
// until there are no more children for this node.
private void getChildren(TreeNode node)
{
TreeNode Node = null;
Category nodeCat = (Category)node.Tag; // get the category for this node
foreach (Category cat in items) // locate all children of this category
{
if (cat.ParentID == nodeCat.ID) // found a child
{
Node = node.Nodes.Add(cat.NodeText); // add the child
Node.Tag = cat; // set its tag to its category
getChildren(Node); // find this child’s children
}
}
}
}
class Category
{
public int ID;
public int ParentID;
public string NodeText;
public Category(int ID, int ParentID, string NodeText)
{
this.ID = ID;
this.ParentID = ParentID;
this.NodeText = NodeText;
}
public override string ToString()
{
return this.NodeText;
}
}
}
