How to expand selected node of tree view in C# in web application form from database with navigate url at run time

Problem is when i expand selected node it will collapse or expand all other nodes

protected void Page_Load(object sender, EventArgs e)
       {
           if (!IsPostBack)
           {
               GetTreeViewItems();



               if (Session["SelNodVal"] != null)
               {

               }
           }
       }

       private void GetTreeViewItems()
       {
           string cs = ConfigurationManager.ConnectionStrings["Data"].ConnectionString;
           SqlConnection con = new SqlConnection(cs);
           SqlDataAdapter da = new SqlDataAdapter("spGetTreeViewItems", con);
           DataSet ds = new DataSet();
           da.Fill(ds);
           ds.Relations.Add("ChildRows", ds.Tables[0].Columns["ID"],
               ds.Tables[0].Columns["ParentId"]);

           foreach (DataRow level1DataRow in ds.Tables[0].Rows)
           {
               if (string.IsNullOrEmpty(level1DataRow["ParentId"].ToString()))
               {
                   TreeNode parentTreeNode = new TreeNode();
                   parentTreeNode.Text = level1DataRow["Name"].ToString();
                   //Session["Name"] = parentTreeNode.Text;

                   // parentTreeNode.NavigateUrl = level1DataRow["URL"].ToString();

                   //parentTreeNode.Expand();
                   //Session["URL"] = parentTreeNode.NavigateUrl;
                   //  parentTreeNode.Collapse();
                   //if (Session["SelNodVal"]== TreeView1.SelectedNode)
                   //{
                   //    TreeView1.SelectedNode.Expanded=true;
                   //}


                   GetChildRows(level1DataRow, parentTreeNode);
                   TreeView1.Nodes.Add(parentTreeNode);
               }
           }
       }
       private void GetChildRows(DataRow dataRow, TreeNode treeNode)
       {
           DataRow[] childRows = dataRow.GetChildRows("ChildRows");

           foreach (DataRow row in childRows)
           {
               TreeNode childTreeNode = new TreeNode();
               childTreeNode.Text = row["Name"].ToString();

               //if (Session["SelNodVal"] != null)
               //{

               //    childTreeNode.Value = Session["SelNodVal"].ToString();
               //    childTreeNode.Expanded = true;
               //}
               //childTreeNode.NavigateUrl = row["URL"].ToString();

               treeNode.ChildNodes.Add(childTreeNode);
               //       childTreeNode.Collapse();
               if (row.GetChildRows("ChildRows").Length > 0)
               {
                   GetChildRows(row, childTreeNode);

               }
           }
       }
       protected void TreeView1_SelectedNodeChanged(object sender, EventArgs e)
       {
           String h = "";
           String u = "";
           String st = TreeView1.SelectedNode.Value;
           string cs = ConfigurationManager.ConnectionStrings["Data"].ConnectionString;
           SqlConnection con = new SqlConnection(cs);
           String qry = "select ID,URL from [vehicle].[dbo].[tblTreeViewItems] where Name = '" + st + "'";
           SqlDataAdapter da = new SqlDataAdapter(qry, con);
           DataSet ds = new DataSet();
           da.Fill(ds);
           if (ds.Tables[0].Rows.Count > 0)
           {
               h = ds.Tables[0].Rows[0]["ID"].ToString();
               u = ds.Tables[0].Rows[0]["URL"].ToString();
           }
           Session["SelNodVal"] = st;
           Response.Redirect(u);
       }

       }
   }