UndoRejected 0 Newbie Poster

hi all
I need help plzzzzzzzzzzzzzzzz
my project uses asp.net and sql database
I use treeview to insert and retrieve hierarchical data from the database
I used the following code the problem is when I added the code for the retrieval the insertion has a problem where I can't add any child to the tree however it was working well before adding that code started from the fill_tree2

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.SqlClient;
//using system.input

public partial class Study_period : System.Web.UI.Page
{

    SqlConnection cn = new SqlConnection(@"Data Source=SONY-PC;Initial Catalog=GP;Integrated Security=True");



    protected void Page_Load(object sender, EventArgs e)
    {
        
        fill_Tree2();
        }
protected void Button1_Click(object sender, EventArgs e)
    {

        try
        {
            cn.Open();
            //string xxx = "insert into ParentTable values('" + TextBox3.Text + "')";
           string xxx = "insert into ParentTable values('" + TextBox3.Text + "','" + DropDownList2.SelectedValue + "')";
            SqlCommand cmd = new SqlCommand(xxx, cn);
            cmd.ExecuteNonQuery();
            cn.Close();
            TreeNode parentnode = new TreeNode(TextBox3.Text);
            TreeView1.Nodes.Add(parentnode);
        }
        catch (SqlException ex)
        {
            Label1.Text = ex.Message;
        }

    }
protected void Button4_Click(object sender, EventArgs e)
    {
       

        String sql = "select ParentID from ParentTable where ParentName ='" + TreeView1.SelectedValue + "'";
        // SqlDataAdapter da = new SqlDataAdapter(sql, cn);
        cn.Open();
        SqlCommand cmd = new SqlCommand(sql, cn);
        int x = Convert.ToInt16(cmd.ExecuteScalar());
        cn.Close();
        Response.Write(x.ToString());
    }

protected void Button3_Click(object sender, EventArgs e)
    {

        String sql = "select ParentID from ParentTable where ParentName='" + TreeView1.SelectedValue + "'   ";
        cn.Open();
        SqlCommand cmd = new SqlCommand(sql, cn);
        int x = Convert.ToInt16(cmd.ExecuteScalar());
        cn.Close();
        x += 0;
        TextBox5.Text = x.ToString();
        string xx = "insert into ChildTable values(" + x + ",'" + TreeView1.SelectedValue + "','" + TextBox4.Text + "','" + DropDownList2.SelectedValue + "')";

        cn.Open();
        SqlCommand cmd1 = new SqlCommand(xx, cn);
        cmd1.ExecuteNonQuery();
        cn.Close();

        TreeNode childnode = new TreeNode(TextBox4.Text);
        TreeView1.SelectedNode.ChildNodes.Add(childnode);
     
    }

   void fill_Tree2()
    {

        DataSet PrSet = PDataset("Select * from ParentTable");

        TreeView1.Nodes.Clear();

        foreach (DataRow dr in PrSet.Tables[0].Rows)
        {

            TreeNode tnParent = new TreeNode();

            tnParent.Text = dr["ParentName"].ToString();

            tnParent.Value = dr["ParentID"].ToString();

            tnParent.PopulateOnDemand = true;

            tnParent.ToolTip = "Click to get Child";

            tnParent.SelectAction = TreeNodeSelectAction.SelectExpand;

            tnParent.Expand();

            tnParent.Selected = true;

            TreeView1.Nodes.Add(tnParent);

            FillChild(tnParent, tnParent.Value);


        }



    }

    public void FillChild(TreeNode parent, string ParentId)
    {
        
        DataSet ds = PDataset("Select * from ChildTable where ParentID =" + ParentId);
      
        parent.ChildNodes.Clear();

        foreach (DataRow dr in ds.Tables[0].Rows)
        {

            TreeNode child = new TreeNode();

            child.Text = dr["ChildName"].ToString().Trim();

            child.Value = dr["ParentID"].ToString().Trim();

            if (child.ChildNodes.Count == 0)
            {
           

                child.PopulateOnDemand = true;

            }

            child.ToolTip = "Click to get Child";

            child.SelectAction = TreeNodeSelectAction.SelectExpand;

            child.CollapseAll();

            parent.ChildNodes.Add(child);

       }
    }



    protected DataSet PDataset(string Select_Statement)
    {
        SqlDataAdapter ad = new SqlDataAdapter(Select_Statement,cn);

        DataSet ds = new DataSet();
        ad.Fill(ds);
        return ds;

    }

}