asp.net分页问题

如何在下列代码中实现，进行if判断如果单击的是button1则执行的是一条sql语句，如果单击的是button2执行的是另外一条sql语句，谢谢
protected void GridView1_PageIndexChanging(object sender, GridViewPageEventArgs e)
    {
        GridView1.PageIndex = e.NewPageIndex;
        string cond = "  and 进仓编号 like " + "'%" + TextBox1.Text.ToString() + "%'";
        string sql = "select  distinct(进仓编号),仓库 from  ck_进仓主表 zb inner join ck_进仓明细 mx on zb.进仓主键=mx.进仓主键" + cond;
        string connString = ConfigurationManager.ConnectionStrings["DepotConnectionString"].ToString();
        SqlConnection conn = new SqlConnection(connString);
        SqlDataAdapter da = new SqlDataAdapter();
        da.SelectCommand = new SqlCommand(sql, conn);
        DataSet ds = new DataSet();
        da.Fill(ds);
        GridView1.DataSource = ds;
        GridView1.AllowPaging = true;
        GridView1.PageSize = 20;
        GridView1.DataBind();
        conn.Close();