Cant access TreeView Node frm Btn Click event after populating frm another click even

[chandrajit_in]

This is very urgent
I am using Visual Studio 2005, TreeView Control.

In aspx page only TreeView Control is create. Code is given below:
---------------------------------------------------------------------
<asp:TreeView runat="server" ID="tvUser" Visible="true">
</asp:TreeView>
--------------------------------------------------------------------

Above treeview is populated in a button click event. Code is given below:
--------------------------------------------------------------------
private void btnUser_Click(object sender, EventArgs e)
{
lblError.Text = string.Empty;
// Execute Stored Procedure and get Node list as DataTable
DataTable moTable = UserMapping.GetUserMapping(Convert.ToInt32(dropProcess.SelectedValue),
Convert.ToInt32(dropTeam.SelectedValue),
Convert.ToInt32(dropSkillType.SelectedValue),
Convert.ToInt32(dropSkillLevel.SelectedValue),
Convert.ToInt32(dropQC.SelectedValue));
tvUser.Nodes.Clear();
chlstuser.Items.Clear();
TreeNode mNode = null;
// ADD ROOT NODE
mNode = new TreeNode();
mNode.Value = dropTeam.SelectedValue + "T";
mNode.Text = dropTeam.SelectedItem.Text;
mNode.ToolTip = dropTeam.SelectedItem.Text;
tvUser.Nodes.Add(mNode);
// ADD CHILD NODE AND OTHER NODE
foreach (DataRow moRow in moTable.Rows)
{
mNode = new TreeNode();
mNode.Value = moRow["inID"].ToString();
mNode.Text = moRow["vcText"].ToString();
mNode.ToolTip = moRow["vcText"].ToString();
mNode.Checked = Convert.ToBoolean(moRow["bolChecked"]);

if ((mNode.Checked))
{
ListItem mListItem = new ListItem(moRow["vcText"].ToString(), moRow["inID"].ToString());
chlstuser.Items.Add(mListItem);
}
string mParentKey = moRow["inParentID"].ToString();

if (mParentKey != "")
{
foreach (TreeNode mSearchNode in tvUser.Nodes)
{
if (mSearchNode.Value == mParentKey)
{
mSearchNode.ChildNodes.Add(mNode);
break;
}
else if (mSearchNode.ChildNodes.Count > 0)
{
AddNodeToTree(mSearchNode, mNode, Convert.ToInt32(mParentKey.Trim()));
}

}

}
}
}

public void AddNodeToTree(TreeNode PresentNode, TreeNode NewNode, Int32 ParentID)
{
if (Convert.ToInt32(PresentNode.Value) == ParentID)
{
PresentNode.ChildNodes.Add(NewNode);
}
else
{
if (PresentNode.ChildNodes.Count > 0)
{
foreach (TreeNode cNode in PresentNode.ChildNodes)
{
AddNodeToTree(cNode, NewNode, ParentID);
}
}
else
{
if (Convert.ToInt32(PresentNode.Value) == ParentID)
{
PresentNode.ChildNodes.Add(NewNode);
}
}
}

}
--------------------------------------------------------------------

Nodes are populated properly.
After populating the nodes I am trying to access all those nodes in another Button Click event in the same page.

Relivant code is
tvUser.Nodes

But this time TreeView is not returning any of the node which are populated in previous Button Click Event.

Its showing tvUser.Nodes.Count = 0
Please let me know, under such a scenario, how shall I get access all those nodes.

Its urgent.... any body please help.
My mail id is chandrajit.samanta 'at' gmail dot com