how to populate treeview?

Question

I have a table \"Category\".It is simply a table of users, where each are identified with a unique UserId and have a corresponding ParentId (pointing to their boss\' UserId). I

Answer 1

If you mean WinForms treeview I would do something like this (error checking skipped):

private void FillTreeView(object sender, EventArgs e)
{
    // create fake datatable
    DataTable dt = new DataTable();
    dt.Columns.Add("UserId",typeof(int));
    dt.Columns.Add("Name",typeof(string));
    dt.Columns.Add("ParentId", typeof(int));


    dt.Rows.Add(new object[] { 3, "Level_1_A", 2 });
    dt.Rows.Add(new object[] { 4, "Level_1_B", 2 });
    dt.Rows.Add(new object[] { 2, "Level_0_A", 0 });
    dt.Rows.Add(new object[] { 5, "Level_2_A", 3 });
    dt.Rows.Add(new object[] { 6, "Level_2_B", 3 });
    dt.Rows.Add(new object[] { 7, "Level_0_B", 0 });
    dt.Rows.Add(new object[] { 8, "Level_1_C", 7 });

    // call recursive function
    AddCurrentChild(0, dt, treeView1.Nodes);
}

private static void AddCurrentChild(int parentId, DataTable dt, TreeNodeCollection nodes)
{
    var rows = dt.Select("ParentId = " + parentId);
    foreach (var row in rows)
    {
        var userId = (int) row["UserId"];
        var name = row["Name"] as string;

        var node = nodes.Add(userId.ToString(), name.ToString());
        node.Tag = row; // if you need to keep a row reference on the node
        AddCurrentChild(userId, dt, node.Nodes);
    }
}