[Solved] How to load TreeView nodes from SqlLite database

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Many thanks to Jdweng for providing a solution.

I modified their code slightly so that it didn’t rely on making the datatable manually and instead took it from my SQLite database file.

Jdweng’s code also made a ‘Root’ node which was not necessary for my application so I changed it to only include the nodes included in my SQLite DB table.

I also needed to change the ‘MakeTree’ method to look for Int64 as I was receiving an error, ‘Specified cast is not valid’ when querying ID and Parent_ID.

using System;
using System.Data;
using System.Data.SQLite;
using System.Linq;
using System.Windows.Forms;

namespace TreeView_SQL_Loader
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            DataTable DT = new DataTable();

            SQLiteConnection sql_con = new SQLiteConnection("data source=\"mydatabase.db\"");
            sql_con.Open();
            SQLiteCommand sql_cmd = sql_con.CreateCommand();
            sql_cmd.CommandText = "SELECT * FROM mytable";
            SQLiteDataAdapter DA = new SQLiteDataAdapter(sql_cmd.CommandText, sql_con);

            DA.Fill(DT);

            sql_con.Close();


            int parentID = 0;
            MakeTree(parentID, treeView1.Nodes, DT);

            treeView1.ExpandAll();
        }

        public void MakeTree(Int64 parentID, TreeNodeCollection parentNode, DataTable DT)
        {
            foreach (DataRow row in DT.AsEnumerable().Where(x => x.Field<Int64>("Field2") == parentID))
            {
                string name = row.Field<string>("Field3");
                Int64 id = row.Field<Int64>("Field1");
                TreeNode node = new TreeNode(name);
                parentNode.Add(node);
                MakeTree(id, node.Nodes, DT);

            }
        }
    }
}

solved How to load TreeView nodes from SqlLite database