protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
        {
            int codigo = 0;

            switch (e.CommandName)
            {
            case "Alterar":
                codigo        = Convert.ToInt32(e.CommandArgument);
                Session["ID"] = codigo;
                Response.Redirect("AlterarCliente.aspx");
                break;

            case "Deletar":
                codigo = Convert.ToInt32(e.CommandArgument);
                UsuariosBD bd = new UsuariosBD();
                bd.Delete(codigo);
                Carrega();
                break;

            default:
                break;
            }
        }