Retain (Keep) Nested Child ASP.Net GridView expanded after PostBack using C# and VB.Net

Hi,

I am using nested datagrids from Nested GridView Example in ASP.Net using C# and VB.Net.

On the inner grid I am allowing the user to delete rows.

However when the page postback I am unable to reopen the row that was opened.

I have tried the code behind to open the row in nested datagrid but is not expanded.

The code was unsuccessful.

How can I have the row expanded when the page posts back?

.aspx

<Columns>
    <%--START SUBGRIDVIEW--%>
    <asp:TemplateField HeaderStyle-HorizontalAlign="Center" ItemStyle-HorizontalAlign="Center">
        <ItemTemplate>
            <img alt="" style="cursor: pointer" src="/img/plus.png" class="ddl_Class_new" />
            <asp:Panel ID="pnlOrders" runat="server" Style="display: none">
                <asp:GridView ID="gv_Child" runat="server"
                    AutoGenerateColumns="false"
                    DataKeyNames="sID"
                    CssClass="mGrid" HorizontalAlign="Center">
                    <Columns>
                    .....
                    </Columns>
                </asp:GridView>
            </asp:Panel>
            <asp:HiddenField ID="IsExpanded" runat="server" />
        </ItemTemplate>
    </asp:TemplateField>
    <%--END SUBGRIDVIEW--%> 
    .....
</Columns>

.cs

protected void btn_Click(object sender, ImageClickEventArgs e)
{
    if (!String.IsNullOrEmpty(Mp.Container.sMt))
    {
        ImageButton imgbtn = (ImageButton)sender;
        GridViewRow row = (GridViewRow)imgbtn.NamingContainer;
 
        HiddenField hiddenField = (HiddenField)row.FindControl("hf_resID");
        string sID_contents = hiddenField.Value.ToString();
 
        string FLabel = row.Cells[3].Text.ToString();
 
        using (MySqlConnection myConnectionString =
          new MySqlConnection(ConfigurationManager.ConnectionStrings["cn"].ConnectionString))
        {
            using (MySqlCommand cmd =
                new MySqlCommand("SP", myConnectionString))
            {
                cmd.Connection.Open();
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.AddWithValue("sID_contents", sID_contents.ToString());
                cmd.ExecuteNonQuery();
                cmd.Connection.Close();
                this.BindData();
 
                if (row.RowType == DataControlRowType.DataRow)
                {
                    HiddenField IsExpanded = (HiddenField)row.FindControl("IsExpanded");
                    IsExpanded.Value = Request.Form[IsExpanded.UniqueID];
                }
 
                Page.ClientScript.RegisterStartupScript(this.GetType(), "Alert", "alert('" + FLabel.ToString() + "');", true);
            }
        }
    }
    else
    {        Page.ClientScript.RegisterStartupScript(this.GetType(), "Alert", "alert('Not enabled');window.location='Default.aspx';", true);
    }
}