i have error in this code ,its urgent

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;
namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        protected DataSet PDataset(string select_statement)
        {
            SqlConnection con = new SqlConnection("server=192.168.0.50\\CIODEVDB;user id=sa;password=epm@3108;database=Parent");
            SqlDataAdapter ad = new SqlDataAdapter(select_statement, con);
            DataSet ds = new DataSet();
            ad.Fill(ds);
            con.Close();
            return ds;
        }


        public void Load_tree2()
        {
            SqlConnection con = new SqlConnection("server=192.168.0.50\\CIODEVDB;user id=sa;password=epm@3108;database=Parent");


            con.Open();

            DataSet ds = PDataset("Select * from details");
            treeView1.Nodes.Clear();
            foreach (DataRow dr in ds.Tables[0].Rows)
            {

                if ((Convert.ToInt32(dr["parentname"].ToString()) == 0))
                {
                    TreeNode tnParent = new TreeNode();
                    tnParent.Text = dr["name"].ToString();
                    string value = dr["id"].ToString();
                    tnParent.Expand();
                    treeView1.Nodes.Add(tnParent);
                    FillChild(tnParent, value);
                    treeView1.ExpandAll();
                }
            }
        }

        public int FillChild(TreeNode parent, string ID)
        {
            SqlConnection con = new SqlConnection("server=192.168.0.50\\CIODEVDB;user id=sa;password=epm@3108;database=Parent");

            con.Open();
            DataSet ds = PDataset("SELECT * FROM details WHERE ParentID =" + ID);
            if (ds.Tables[0].Rows.Count > 0)
            {

                foreach (DataRow dr in ds.Tables[0].Rows)
                {
                    TreeNode child = new TreeNode();
                    child.Text = dr["name"].ToString().Trim();
                    string temp = dr["id"].ToString();
                    child.Collapse();
                    parent.Nodes.Add(child);
                    FillChild(child, temp);
                }
                return 0;
            }
            else
            {
                return 0;
            }

        }

        private void Form1_Load(object sender, EventArgs e)
        {
            Load_tree2();

        }

        private void btnadd_Click(object sender, EventArgs e)
        {
            SqlConnection con = new SqlConnection("server=192.168.0.50\\CIODEVDB;user id=sa;password=epm@3108;database=Parent");

            con.Open();


            string MyString = "INSERT INTO details(name,parentname)values('" + textBox1.Text + "'," + getNodeid(treeView1.SelectedNode.ToString()) + ")";

            SqlCommand MyCmd = new SqlCommand(MyString, con);


            MyCmd.ExecuteNonQuery();

            TreeNode childnode = new TreeNode(textBox1.Text);
            treeView1.SelectedNode.Nodes.Add(childnode);
            treeView1.ExpandAll();
            textBox1.Clear();
            con.Close();
            Load_tree2();
            textBox1.Clear();

        }

        private int getNodeid(string nodename)
        {
            string node = nodename.Substring(10);
            SqlConnection con = new SqlConnection("server=192.168.0.50\\CIODEVDB;user id=sa;password=epm@3108;database=Parent");
            con.Open();
            string MyString = "select ID from details where name='" + node + "'";

            SqlCommand MyCmd = new SqlCommand(MyString, con);
            SqlDataAdapter da = new SqlDataAdapter(MyCmd);
            DataTable dt = new DataTable();
            da.Fill(dt);
            string aa = dt.Rows[0][0].ToString();

            con.Close();
            return Convert.ToInt32(aa);

        }

        private void btnremove_Click(object sender, EventArgs e)
        {
            SqlConnection con = new SqlConnection("server=192.168.0.50\\CIODEVDB;user id=sa;password=epm@3108;database=Parent");
            con.Open();

            string MyString = "Delete from details where name= '" + treeView1.SelectedNode.ToString() + "'";

            SqlCommand MyCmd = new SqlCommand(MyString, con);
            SqlDataAdapter da = new SqlDataAdapter(MyCmd);
            MyCmd.ExecuteNonQuery();
            Load_tree2();

            con.Close();
            //treeView1.SelectedNode.Remove();
        }





        private void btnparent_Click(object sender, EventArgs e)
        {
            SqlConnection con = new SqlConnection("server=192.168.0.50\\CIODEVDB;user id=sa;password=epm@3108;database=Parent");
            con.Open();
            string MyString = "INSERT INTO details(name)values('" + textBox1.Text + "')";
            SqlCommand MyCmd = new SqlCommand(MyString, con);
            TreeNode parentnode = new TreeNode(textBox1.Text);
            treeView1.SelectedNode.Nodes.Add(parentnode);
            MyCmd.ExecuteNonQuery();

            con.Close();
            textBox1.Clear();
        }
    }
}