How to find Parent page Dropdownlist in childpage and auto refresh

 protected void BtnSave_Click(object sender, EventArgs e)
        {
            if (BtnSave.Text == "Save")
            {
                Save();
                Message("Data Inserted Successfully .!");
                DropDownList DdlGroup = (DropDownList)this.Parent.FindControl("ddlGroup");
                if (DdlGroup != null)
                {
                    List<UFMS_Group> listGroup = new List<UFMS_Group>();
                    listGroup = UERPManagement.GetInstance.GetAllGroups();
                    var lnqGroup = from grp in listGroup

                                   select grp;
                    DdlGroup.DataSource = lnqGroup.ToList();
                    DdlGroup.DataTextField = "Group_Name";
                    DdlGroup.DataValueField = "Group_ID";
                    DdlGroup.DataBind();
                    DdlGroup.Items.Insert(0, UserCommand.Select.ToString());
                }
            }

            else
            {
                update();
                //FillGridViewGroup();
                Message("Data Updated Successfully .!");
            }
        }