adding dynamic usercontrol to the popUp

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C#

ASP.NET

hello , i am adding user controls to a form by selecting a dropdown items
when i clicking a insert button on each user control for first time is not working but for the second time is working

what can i doing?
user control page_load

protected void Page_Load(object sender, EventArgs e)
{
    try
    {
        //if ( IsPostBack)
        //    return;


        if (Request.QueryString["ctc"] != null)
        {
            HIDctg_Id.Value = Request.QueryString["ctc"];
        }
        if (Request.QueryString["id"] != null)
        {
            hdnID.Value = Request.QueryString["id"].ToString();
            Equipment.Entities.eqp_IEC600441ClassP  _iec = _eqp_IEC600441ClassPService.FindByiec_Id (Convert.ToInt64(hdnID.Value));
            _eqp_IEC600441ClassP = _iec;
            eqp_IEC600441ClassP = _iec;

        }
        else
        {
            hdnID.Value = "0";
            BTNDelete.Visible = false;

        }

    }
    catch
    {
    }
  }

form code :::

protected override void OnLoad(EventArgs e)
 {

         base.OnLoad(e);

             CreateStandardsCoreUC();

 }
 public void CreateStandardsCoreUC() {
     if (ddl_CoresStandards.SelectedValue != "select")
     {
         Control uc = (Control)Page.LoadControl(getUserControl(ddl_CoresStandards.SelectedValue));
         pnlUC.Controls.Add(uc);

     }

 }