Fill TreeView Dynamically... Like Category > Parent Category

Question

Here i have made some code to get my categories in TreeView like --Core ---Core Subcat --Non Core ---Non Core Subcat

My code only shows me:

1. Core
2. Non Core

Please help me out with this code. please correct me if i'm wrong.

Thank You.

SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["InventoryManagerConnectionString"].ConnectionString);

        private void btnLoadNodes_Click(object sender, EventArgs e)
        {

            DataTable dt = this.GetData("SELECT * FROM tblProductCategories WHERE Cat_ParentCat =0");
            this.PopulateTree(dt, 0, null);

        }

        private void PopulateTree(DataTable dtParent, int parentId, TreeNode treeNode)
        {
            foreach (DataRow row in dtParent.Rows)
            {
                TreeNode child = new TreeNode
                {
                    Text = row["Cat_Name"].ToString(),
                    Tag = row["Cat_ID"]
                };
                if (parentId == 0)
                {
                    treeViewCat.Nodes.Add(child);
                    DataTable dtChild = this.GetData("SELECT * FROM tblProductCategories WHERE Cat_ParentCat="+ child.Tag);
                }
                else
                {
                    treeNode.Nodes.Add(child);
                }
            }
        }

        private DataTable GetData(string query)
        {
            DataTable dt = new DataTable();

            SqlCommand cmd = new SqlCommand(query);

            SqlDataAdapter sda = new SqlDataAdapter();

            cmd.CommandType = CommandType.Text;
            cmd.Connection = con;
            sda.SelectCommand = cmd;
            sda.Fill(dt);
            return dt;

        }

Result Expected in TreeView:

-Core
--Core Subcat
-Non Core
--Non Core Subcat

Answer 1

I think its better that you change your "Sql Select". If you get your data in TreeView model, you can show it very simple.

In this sample "rn" field will help you so much.

Answer 2

public partial class TreeTest : Form
{
    public TreeTest()
    {
        InitializeComponent();

        SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["InventoryManagerConnectionString"].ConnectionString);



        var dt = new DataTable();
        var source = dt.AsEnumerable();

        var nodes = GetTreeNodes(
            /*The data table*/
            source,
            /*How detect if a row is a root row*/
            (r) => r.Field<int>("Cat_ParentCat") == 0,
            /*How to find child rows for a row*/
            (r, s) => s.Where(x => r["Cat_ID"].Equals(x["Cat_ParentCat"])),
            /*How to create a node from a row*/
            (r) => new TreeNode { 
            Text = r.Field<string>("Cat_Name"),
           Tag = r.Field<int>("Cat_ID")
    }
    );
            treeViewCat.Nodes.AddRange(nodes.ToArray());
    }

    SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["InventoryManagerConnectionString"].ConnectionString);

    private void btnLoadNodes_Click(object sender, EventArgs e)
    {
        string query = "SELECT * FROM tblProductCategories WHERE Cat_ParentCat =0";
        GetData(query);
    }


    public DataTable GetData( string command)
    {
        var dt = new DataTable();
        using (var da = new SqlDataAdapter(command, con))
            da.Fill(dt);
        return dt;
    }


        private IEnumerable<TreeNode> GetTreeNodes<T>(
            IEnumerable<T> source,
            Func<T, Boolean> isRoot,
            Func<T, IEnumerable<T>, IEnumerable<T>> getChilds,
            Func<T, TreeNode> getItem)
        {
            IEnumerable<T> roots = source.Where(x => isRoot(x));
            foreach (T root in roots)
                yield return ConvertEntityToTreeNode(root, source, getChilds, getItem); ;
        }
    private TreeNode ConvertEntityToTreeNode<T>(
        T entity,
        IEnumerable<T> source,
        Func<T, IEnumerable<T>, IEnumerable<T>> getChilds,
        Func<T, TreeNode> getItem)
    {
        TreeNode node = getItem(entity);
        var childs = getChilds(entity, source);
        foreach (T child in childs)
            node.Nodes.Add(ConvertEntityToTreeNode(child, source, getChilds, getItem));
        return node;
    }


    private void btnGetNode_Click(object sender, EventArgs e)
    {
        try
        {
            MessageBox.Show(treeViewCat.SelectedNode.Tag.ToString());
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
    }

}