How to hide an empty databound dropdownlist

private string GetConnectionString(){
       //calling the connection string that was set up from the web config file
        return ConfigurationManager.ConnectionStrings["DBConnection"].ConnectionString;
}

private void BindDropDownList(){
           DataTable dt = new DataTable();
           using (SqlConnection sqlConn = new SqlConnection(GetConnectionString())){
                string sql = "SELECT Field1, Field2 FROM YourTable WHERE Field3 = @Param1";
                using(SqlCommand sqlCmd = new SqlCommand(sql,sqlConn)){
                    sqlCmd.Parameters.AddWithValue("@Param1", "YourFilterValueHere");
                    sqlConn.Open();
                    using(SqlDataAdapter sqlAdapter = new SqlDataAdapter(sqlCmd))
                    {
                        sqlAdapter.Fill(dt);
                    }
                }
            }

            if (dt.Rows.Count > 0)
            {
                DropDownList1.DataSource =dt;
                DropDownList1.DataTextField = "Field2"; // the items to be displayed in the list items
                DropDownList1.DataValueField = "Field1"; // the id of the items displayed
                DropDownList1.DataBind();
            }
            else
            {
                  DropDownList1.Visible = false;
            }
       
}


protected void Page_Load(object sender, EventArgs e){
        if (!IsPostBack)
            BindDropDownList();
}