How to remain the treeview after redirect to another page?

Question

Im currently using this method to bind my treeview, After i expand the treeview and click the node, it will redirect to another page, and then the treeview will be refresh to default, which means showing the treeview before expanding.. so i need to save the treeview state in order to remain the treeview state. i had tried the below method but it's not working, anyone can help..

protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
if (Session["ExpandedNodes"] != null)
{
((List<string>)Session["ExpandedNodes"]).ForEach(a => TreeView1.FindNode(a).Expanded = true);
}
LoadTransactionMenu();
}
}
private void LoadTransactionMenu()
{
//TRANSACTION MENU // this is used to bind the data to the treeview
string SubModuleID, SubModuleNM, DocModuleID, DocModuleName, MenuTransID, MenuTransName;
SqlConnection con = new SqlConnection(ConString);
string CmdString = "SELECT SUBMODULEID, SUBMODULENM, URLNAME FROM SUBMODULE";
SqlCommand cmd = new SqlCommand(CmdString, con);
SqlDataAdapter sda = new SqlDataAdapter(cmd);
DataTable dt = new DataTable();
sda.Fill(dt);
TreeNode node1 = new TreeNode();
node1.Text = "TRANSACTION MENU";
TreeView1.Nodes.Add(node1);
for (int i = 0; i < dt.Rows.Count; i++)
{
SubModuleID = dt.Rows[i]["SUBMODULEID"].ToString();
SubModuleNM = dt.Rows[i]["SUBMODULENM"].ToString();
TreeNode SubModuleNode = new TreeNode(SubModuleNM, SubModuleID);
SubModuleNode.NavigateUrl = dt.Rows[i]["URLNAME"].ToString();
node1.ChildNodes.Add(SubModuleNode);
CmdString = "SELECT DDID, DOCNAME, DDADDRESS FROM DOCMODULE WHERE SUBMODULEID=@SUBMODULEID";
cmd = new SqlCommand(CmdString, con);
cmd.Parameters.AddWithValue("@SUBMODULEID", SubModuleID);
sda = new SqlDataAdapter(cmd);
DataTable dt2 = new DataTable();
sda.Fill(dt2);
for (int j = 0; j < dt2.Rows.Count; j++)
{
DocModuleID = dt2.Rows[j]["DDID"].ToString();
DocModuleName = dt2.Rows[j]["DOCNAME"].ToString();
TreeNode DocModuleNode = new TreeNode(DocModuleName, DocModuleID);
DocModuleNode.NavigateUrl = dt2.Rows[j]["DDADDRESS"].ToString();
SubModuleNode.ChildNodes.Add(DocModuleNode);
CmdString = "SELECT DID, DNAME, DADDRESS FROM MENUTRANSACTION WHERE DDID=@DDID AND UID= '" + Session["UserID"] + "'";
cmd = new SqlCommand(CmdString, con);
cmd.Parameters.AddWithValue("@DDID", DocModuleID);
sda = new SqlDataAdapter(cmd);
DataTable dt3 = new DataTable();
sda.Fill(dt3);
for (int k = 0; k < dt3.Rows.Count; k++)
{
MenuTransID = dt3.Rows[k]["DID"].ToString();
MenuTransName = dt3.Rows[k]["DNAME"].ToString();
TreeNode MenuTransNode = new TreeNode(MenuTransName, MenuTransID);
MenuTransNode.NavigateUrl = dt3.Rows[k]["DADDRESS"].ToString();
DocModuleNode.ChildNodes.Add(MenuTransNode);
}
if (DocModuleNode.ChildNodes.Count == 0)
{
SubModuleNode.ChildNodes.Remove(DocModuleNode);
}
}
if (SubModuleNode.ChildNodes.Count == 0)
{
node1.ChildNodes.Remove(SubModuleNode);
}
}
}
protected void TreeView1_SelectedNodeChanged(object sender, EventArgs e)
{
List<string> expandedNodes = new List<string>();
//get all expanded nodes
TreeView1.Nodes.Cast<TreeNode>().ToList().ForEach(a => GetExpandedStatus(a, expandedNodes));
//collapse all to reset the treeview
TreeView1.CollapseAll();
//save expanded node value paths
Session["ExpandedNodes"] = expandedNodes;
}
public void GetExpandedStatus(TreeNode node, List<string> ExpandedNodes)
{
//check if node is expanded
if (node.Expanded.GetValueOrDefault(false))
ExpandedNodes.Add(node.ValuePath);
node.ChildNodes.Cast<TreeNode>().ToList().ForEach(a => GetExpandedStatus(a, ExpandedNodes));
}