批量删除, 没选择弹出"请选择" ,能弹,但是弹出N个.该怎么处理

批量删除, 没选择弹出"请选择" ,能弹,但是弹出N个.
当前页面FindControl得到N个记录,就弹出N次"请选择"

很烦人, 弹出一个就够了啊..

C# code

       SqlAA da=new SqlAA();       protected void deleteAll_Click(object sender, EventArgs e)        {            for (int i = 0; i < GridView1.Rows.Count; i++)            {                CheckBox cbox = (CheckBox)GridView1.Rows[i].FindControl("CheckBox1");                               string sqlstr = "delete from Photo where PhotoID='" + GridView1.DataKeys[i].Value + "'";                //调用公共类中的 DoSql方法执行删除操作的SQL语句                bool delete = da.DoSql(sqlstr);                if (cbox.Checked == true)                {                    if (delete)                    {                        Response.Write("<script language=javascript>alert('批量删除成功！');location='Photo.aspx'</script>");                    }                }                else                {                        Response.Write("<script language=javascript>alert('请选择！')</script>");                }            }        }